diff --git a/eslint.config.js b/eslint.config.js
index 55e792b2..e4da029a 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -76,7 +76,6 @@ export default tseslint.config(
         },
       ],
       "@typescript-eslint/no-import-type-side-effects": "error",
-      "@typescript-eslint/no-non-null-assertion": "off",
       "@typescript-eslint/no-shadow": "error",
       "@typescript-eslint/no-unnecessary-parameter-property-assignment":
         "error",
diff --git a/src/index.ts b/src/index.ts
index f0056ada..4a6fd248 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -75,8 +75,8 @@ const manualOpenGallery = new ImageLightbox(
 );
 document
   .getElementsByClassName("trigger_lightbox")
-  .item(0)!
-  .addEventListener("click", () => {
+  .item(0)
+  ?.addEventListener("click", () => {
     manualOpenGallery.open();
   });
 
@@ -89,13 +89,13 @@ const dynamicAddingGallery = new ImageLightbox(
 );
 document
   .getElementsByClassName("add_image")
-  .item(0)!
-  .addEventListener("click", () => {
+  .item(0)
+  ?.addEventListener("click", () => {
     const linkContainer = document
       .getElementsByClassName("demo_dynamic")
-      .item(0)!;
+      .item(0);
     const newLi = document.createElement("li");
-    linkContainer.appendChild(newLi);
+    linkContainer?.appendChild(newLi);
 
     const newAnchor = document.createElement("a");
     newAnchor.dataset["imagelightbox"] = "i";
diff --git a/src/lib/ImageView.ts b/src/lib/ImageView.ts
index edecf768..4ef881cf 100644
--- a/src/lib/ImageView.ts
+++ b/src/lib/ImageView.ts
@@ -38,11 +38,17 @@ export function ImageView(
   containerElement.classList.add("ilb-image-container");
   let isVideoPreloaded: boolean | undefined = undefined;
 
-  const isVideo = image.dataset["ilb2Video"] !== undefined;
+  const videoId = image.dataset["ilb2VideoId"];
+  let isVideo =
+    image.dataset["ilb2Video"] !== undefined && videoId !== undefined;
   if (isVideo) {
-    [imageElement, isVideoPreloaded] = videoCache.element(
-      image.dataset["ilb2VideoId"]!,
-    );
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- Checked by the if above
+    const videoElement = videoCache.element(videoId!);
+    if (videoElement !== undefined) {
+      [imageElement, isVideoPreloaded] = videoElement;
+    } else {
+      isVideo = false;
+    }
   }
   containerElement.appendChild(imageElement);
 
diff --git a/src/lib/PreloadedVideo.ts b/src/lib/PreloadedVideo.ts
index e5ff0081..4743bf63 100644
--- a/src/lib/PreloadedVideo.ts
+++ b/src/lib/PreloadedVideo.ts
@@ -1,7 +1,6 @@
 import type { VideoOptions } from "./interfaces/VideoOptions";
 
 export interface PreloadedVideo {
-  dimensions(): [number, number];
   element(): [HTMLVideoElement, boolean];
   id(): string;
 }
@@ -24,8 +23,6 @@ export function PreloadedVideo(
   videoElement.dataset["ilb2VideoId"] = videoId;
   let isLoaded = false;
   let autoplay = false;
-  let height: number | undefined = undefined;
-  let width: number | undefined = undefined;
 
   for (const [key, value] of Object.entries(videoOptions)) {
     switch (key) {
@@ -40,12 +37,6 @@ export function PreloadedVideo(
       case "src":
         videoElement.setAttribute(key, (value as number | string).toString());
         break;
-      case "height":
-        height = value as number;
-        break;
-      case "width":
-        width = value as number;
-        break;
       default:
     }
   }
@@ -66,10 +57,6 @@ export function PreloadedVideo(
     return videoId;
   }
 
-  function dimensions(): [number, number] {
-    return [width ?? videoElement.width, height ?? videoElement.height];
-  }
-
   function element(): [HTMLVideoElement, boolean] {
     if (autoplay) {
       if (isLoaded) {
@@ -82,7 +69,6 @@ export function PreloadedVideo(
   }
 
   return {
-    dimensions,
     element,
     id,
   };
diff --git a/src/lib/State.ts b/src/lib/State.ts
index 639a81cf..2a580c82 100644
--- a/src/lib/State.ts
+++ b/src/lib/State.ts
@@ -87,7 +87,10 @@ export function State(
     transitionDirection: TransitionDirection,
     callback?: () => void,
   ): void {
-    const oldImageView = currentImageView!;
+    if (currentImageView === null) {
+      return;
+    }
+    const oldImageView = currentImageView;
     oldImageView.transitionOut(transitionDirection, () => {
       oldImageView.removeFromDOM();
       callback?.();
@@ -107,7 +110,10 @@ export function State(
 
   function addNewImage(transitionDirection: TransitionDirection): void {
     currentImageView?.addToDOM(transitionDirection, () => {
-      const image = targetImages[currentImage!];
+      if (currentImage === null) {
+        return;
+      }
+      const image = targetImages[currentImage];
       if (options.caption) {
         setCaption(
           image.dataset["ilb2Caption"] ??
@@ -117,8 +123,8 @@ export function State(
         );
       }
       transitionInNewImage();
-      if (options.preloadNext && currentImage! + 1 < targetImages.length) {
-        const nextImage = targetImages[currentImage! + 1];
+      if (options.preloadNext && currentImage + 1 < targetImages.length) {
+        const nextImage = targetImages[currentImage + 1];
         const nextImageElement = document.createElement("img");
         nextImageElement.setAttribute(
           "src",
diff --git a/src/lib/VideoCache.ts b/src/lib/VideoCache.ts
index 368f822f..ee9ebe6c 100644
--- a/src/lib/VideoCache.ts
+++ b/src/lib/VideoCache.ts
@@ -4,8 +4,7 @@ import { PreloadedVideo } from "./PreloadedVideo";
 
 export interface VideoCache {
   add(elements: Array<HTMLAnchorElement>): void;
-  dimensions(videoId: string): [number, number] | undefined;
-  element(videoId: string): [HTMLVideoElement, boolean];
+  element(videoId: string): [HTMLVideoElement, boolean] | undefined;
 }
 
 export function VideoCache(): VideoCache {
@@ -23,22 +22,13 @@ export function VideoCache(): VideoCache {
     }
   }
 
-  function dimensions(videoId: string): [number, number] | undefined {
+  function element(videoId: string): [HTMLVideoElement, boolean] | undefined {
     const video = videos.find((x) => x.id() === videoId);
-    if (video === undefined) {
-      return undefined;
-    }
-    return video.dimensions();
-  }
-
-  function element(videoId: string): [HTMLVideoElement, boolean] {
-    const video = videos.find((x) => x.id() === videoId)!;
-    return video.element();
+    return video?.element();
   }
 
   return {
     add,
-    dimensions,
     element,
   };
 }
diff --git a/src/lib/navigation.ts b/src/lib/navigation.ts
index 054dc36b..4b8aa4a7 100644
--- a/src/lib/navigation.ts
+++ b/src/lib/navigation.ts
@@ -7,7 +7,7 @@ navigation.classList.add("ilb-navigation");
 
 export function addNavigationItems(
   images: Array<HTMLAnchorElement>,
-  currentIndex: () => number | null,
+  currentIndexFn: () => number | null,
   change: (index: number, transitionDirection: TransitionDirection) => void,
   animationSpeed: number,
 ): void {
@@ -16,15 +16,20 @@ export function addNavigationItems(
     const button = document.createElement("button");
     button.style.transition = `background-color ${animationSpeed.toString()}ms ease`;
     const buttonClick = (): void => {
-      if (button.classList.contains("ilb-navigation-active")) {
+      const currentIndex = currentIndexFn();
+      if (
+        button.classList.contains("ilb-navigation-active") ||
+        currentIndex === null ||
+        button.parentNode === null
+      ) {
         return;
       }
       const buttonIndex = Array.prototype.indexOf.call(
-        button.parentNode!.childNodes,
+        button.parentNode.childNodes,
         button,
       );
       const loadDirection =
-        buttonIndex < currentIndex()!
+        buttonIndex < currentIndex
           ? TransitionDirection.Left
           : TransitionDirection.Right;
       change(buttonIndex, loadDirection);
@@ -46,13 +51,16 @@ export function changeNavigationCurrent(currentIndex: number): void {
 
 export function addNavigationToDOM(
   images: Array<HTMLAnchorElement>,
-  currentIndex: () => number | null,
+  currentIndexFn: () => number | null,
   change: (index: number, transitionDirection: TransitionDirection) => void,
   animationSpeed: number,
 ): void {
   navigation.textContent = "";
-  addNavigationItems(images, currentIndex, change, animationSpeed);
-  changeNavigationCurrent(currentIndex()!);
+  addNavigationItems(images, currentIndexFn, change, animationSpeed);
+  const currentIndex = currentIndexFn();
+  if (currentIndex !== null) {
+    changeNavigationCurrent(currentIndex);
+  }
   getContainer().appendChild(navigation);
 
   navigation.addEventListener("click", (e) => {