Fix gaps in the fullscreen bar (#2066)

Author: MortimerGoro

app/src/main/res/layout/navigation_bar_fullscreen.xml

@@ -6,6 +6,7 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center"
+        android:background="@drawable/resize_bar_background"
         android:visibility="gone">
 
         <FrameLayout