Crash when trying to perform Weld from hotkey with hidden mesh selected

[misaki-eymard]

Description:
If you try to rperformn Weld by pressing the Weights - Weld All or Weights - Weld Overlapping hotkey while a hidden mesh attachment is selected, the Spine Editor crashes.

Expected behavior:
Since the Weld button cannot be pressed while a hidden mesh attachment is selected on the Weights view, it seems correct that hotkeys related to Weld should be disabled while a hidden mesh attachment is selected as well.

Steps to reproduce:

1. The two hotkeys Weights - Weld All and Weights - Weld Overlapping hotkeys have no keys assigned by default, so assign any key you wish in the hotkeys.txt file.
2. Open the Spineboy project in Spine 4.2.39.
3. Select the mouth-grind attachment in the mouth slot. (Unless you have made changes, this attachment should be hidden in setup mode).
4. Press the hotkey you set in step 1. Then the editor crashes.

The versions of Spine that can reproduce this issue:
Spine 4.2.39

This issue was reported in the following thread on the forum:
https://esotericsoftware.com/forum/d/28059-drag-n-drop-crash