Existing/Global palette isn't initialized properly on first time opening TEXTUREx editor

[ninesphere]

SLADE Version: (3.2.2) Operating System: Windows

Issue Details: When opening the TEXTUREx editor for the first time, if the palette is set to Existing/Global, all textures will display incorrectly using only grayscale colors:

However, simply changing the palette to something else and then back (for instance, quickly scrolling down to Adrenix and then back to Existing/Global) fixes this issue, as does closing and re-opening the TEXTUREx editor.