bugfix-library - Fix mobile crash on library browse scroll

[mattsigal]

Pull Request

Summary

Fix an unhandled crash on mobile clients when opening a library and scrolling in vertical/horizontal mode past the initial pull. The crash was caused by accessing disposed FocusNodes in QuickReturnWrapper during initial library page load reset, alongside missing bounds checks in SliverChildBuilderDelegate. It seems isolated to mobile.

Related Issues

Link related issues or tickets separated by commas.

• Closes #
• Fixes #
• Related to #

Type of Change

• Bug fix
• New feature
• Refactor
• Performance improvement
• UI/UX update
• Documentation update
• Build/CI change
• Other (describe):

Changes Made

List the key changes included in this PR.

• library_browse_screen.dart: Checked _vm.items.isNotEmpty before passing getGridItemFocusNode(0) to QuickReturnWrapper, preventing QuickReturnWrapper from holding a reference to a FocusNode disposed by cleanupGridFocusNodes(0).
• library_browse_screen.dart: Added bounds checks if (index < 0 || index >= itemsToDisplay.length) return null; inside SliverChildBuilderDelegate for vertical and horizontal grid layouts. Added _scrollController.hasClients guards in _nearGridEnd and horizontal scroll listener.
• quick_return_wrapper.dart: Added canRequestFocus check on topFocusNode before requesting focus in _returnToStart().

Platform

• Android
• iOS
• tvOS
• Web
• macOS
• Windows
• Linux
• All / Shared code

Testing

Describe how this change was tested.

• Tested on emulator / simulator
• Tested on physical device
• Manual testing completed - Tested on Pixel 10 Pro (also where the bug was found)
• Not tested (explain why):

Test Steps

1. Launch Moonfin on an Android mobile device (or compact screen mode).
2. Open any library (e.g., Movies, TV Shows) without applying Group By filters first.
3. Verify the library loads smoothly on initial page load in both vertical and horizontal scroll orientation without crashing.
4. Scroll to the bottom of the grid and verify infinite scroll loads additional pages smoothly.

Screenshots (if applicable)

Include screenshots or recordings for UI changes.

Checklist

• Code builds successfully
• Code follows project style and conventions
• No unnecessary commented-out code
• No new warnings introduced