_reset_time_scales() has a visibility guard that was originally needed
to prevent resets on session start. After 4e06e305bf scoped the call to
only run when all sessions end, the guard is unnecessary and prevents
the speed state from being properly reset.
Replace is_visible_in_tree() with an is_inside_tree() guard on the UI
update only, to avoid theme access warnings while still allowing the
state reset when the Game tab is not active.
Also includes a fix to the reset-to-1.0x button, which will now always be
disabled if the speed is already 1.0x.
Fixes#115400.
Max Aller
d66c9cfeba