SpTabLayout causes errors when switching Pharo theme

[JanBliznicenko]

Whenever a window with SpTabLayout is open (or even closed, but still in memory), Pharo theme cannot be changed, or changes just paritally, and ends up in an error.

Example:

| previousTheme newTheme |
Smalltalk garbageCollect.
SpExampleBrowser open.
previousTheme := Smalltalk ui theme class.
newTheme := (previousTheme isKindOf: PharoDarkTheme) ifTrue: [ PharoLightTheme ] ifFalse: [ PharoDarkTheme ].
newTheme beCurrent.
previousTheme beCurrent.

Confirmed the issue to be present in all versions of Pharo (tested in 11-13). In Pharo 13, use build 299 or earlier, as there is another issue at the moment, preventing the SpExampleBrowser from opening, since build 300 (#1631).

Tested on Windows 11.