Fixing an imgui-related crash related to debug errors

[katemonster33]

Summary

Bugfixes "When a debug error is thrown during drawing, imgui itself throws an exception, crashing the game"

Purpose of change

When draw errors happen, we expect to see the debug message. Instead, CDDA crashes. This prevents this
Fixes: #72047

Describe the solution

Added a boolean in ui_manager.cpp to prevent cataimgui::client::new_frame to be called twice in a row

Describe alternatives you've considered

Could have added the boolean inside cataimgui::client::new_frame but currently there are multiple definitions, for curses and SDL. This bypasses needing to make the same change in 2 places

Testing

Loaded the save specified in the linked issue and verified the debug error is shown

Additional context

[github-actions]

Auto-requesting reviews from non-collaborators: @Qrox

[Qrox]

When a debug message is thrown and dismissed, the ui_manager code will restart drawing all windows to resume the content overwritten by the debug message. Will this cause the UI to contain extra elements due to it drawing an ImGUI window multiple times in a single frame?

[katemonster33]

@Qrox hmm, im not sure. I guess I would need some way of making that behavior happen with an ImGui window on screen. I could see it being possible.