UI hard crashes when adding file in certain circumstances

[intvsteve]

When dragging a ROM from the ROM list to the menu layout, the UI crashes with a NullReferenceException.

Operating system version

Windows (all versions)

Program version (from About box)

All versions

Expected behavior

It doesn't crash. :P Two expected outcomes:

• Don't allow the drop
• If target of drop is OK, then allow it and don't crash

Actual behavior

Crash! (NullReferenceException)

Steps to reproduce

1. Fill up the root of the Menu Layout with 255 items -- at least one must be a folder!
2. Drag a ROM from the ROMs list to a folder that does not have 255 items in it

Crash log if available (paste or attach)

ErrorLog_2020-08-09-11-26-51-769.txt

[intvsteve]

The bug is triggered in the Windows drag/drop code in FileNodeViewModel.WPF.cs in which it fails to correctly get the menu layout object to save changes to.

[intvsteve]

WORKAROUND

1. In the root folder, remove a ROM
2. Now things should work

It's possible this bug is not specific to the root folder being full - need to verify if it also happens with a folder that has 255 items, one of which is a folder, and the same kind of action is attempted.