Make invisible `SplitContainer` nodes correctly calculate the minimal size of its children
Make invisible `SplitContainer` nodes correctly calculate the minimal size of its children

(cherry picked from commit e4d56e4c62e86a78246ca0d250ca6d52adbd94bf)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot