Calling hide() on a hidden button generates a spurious unhover event

[retsyx]

Describe the bug
Hiding a button unconditionally generates an unhover event.

To Reproduce
Steps to reproduce the behaviour:

1. Call hide() on a button
2. Call hide() again
3. See unhover event from button

Expected behaviour
Calling hide() on an already hidden button should not generate any incorrect events.

Screenshots

N/A

Platform and software (please complete the following information):

• OS: Linux
• Pygame GUI version - latest
• Pygame version - latest

Additional context

This may apply to other UI elements. Not tested.

This bug forces checking visibility on UI elements before calling hide() to avoid triggering these incorrect events.

[rbaltrusch]

Hi @MyreMylar, could you assign me this issue and review my PR? It should fix this issue for all widgets in the code base.

However, in my opinion, there is a related and more complicated issue here that I am not fixing with this PR that might need additional work: the method on_unhovered can get called without the hovered state actually being set (due to that state being independently handled outside of that method), which partially leads to the issue described here. It would make more sense to not be able to unhover if already unhovered.