UIListBox - add option for always one item selected (use in drop down)

[Toma400]

Describe the bug While selecting listbox entry, their recognition works randomly, unless I un-select the entry (in such case, recognition is fully reliable).

To Reproduce Steps to reproduce the behaviour:

1. Create listbox and some variable to store listbox output (name of element chosen), so event.text won't be empty
2. Create event system which overwrites variable with current event.text when entry is clicked, and with None when it is unclicked
3. Let the program print the entry name when you click on button and variable value is not None

Expected behaviour App should print entry name no matter how I clicked on it - be it by un-selecting, on simply switching from one entry to another.

Screenshots Video instead: https://user-images.githubusercontent.com/65849429/204492359-ee0edac7-80b1-4965-9c3b-867f44ef9001.mp4

Platform and software (please complete the following information):

• OS: Windows 10
• Pygame GUI version: 0.6.4, 0.6.5 (tested on both)
• Pygame version [e.g. 2.0.0, 2.1.0]

Additional context Workspace on which I worked on - L12/L27/L29 is variable system allowing me to store text passed from listbox, on L34 I try to print it when correct button is clicked and entry is selected