fix: Fixed ArgumentException when using DropdownStyle outside of OnGUI

Author: SolidAlloy

Editor/TypeDropdown/DropdownStyle.cs

@@ -47,7 +47,10 @@ internal static class DropdownStyle
             onNormal = { textColor = Color.white }
         };
 
-        public static readonly GUIStyle SearchToolbarStyle = new GUIStyle(GUI.skin.FindStyle("ToolbarSeachTextField"));
+        private static GUIStyle _searchToolbarStyle;
+
+        public static GUIStyle SearchToolbarStyle =>
+            _searchToolbarStyle ?? (_searchToolbarStyle = new GUIStyle(GUI.skin.FindStyle("ToolbarSeachTextField")));
 
         private static readonly Color HighlightedColorDarkSkin = new Color(1f, 1f, 1f, 0.028f);
         private static readonly Color HighlightedColorLightSkin = new Color(1f, 1f, 1f, 0.3f);