This fixes a cosmetic issue where the tooltip got 'stuck' as long as you
kept moving your mouse around. The trade-off is it more often than not
fades out quicker than it did before, but I believe this isn't a problem.
This prevents the tooltip fade-out animation getting the 500ms delay unless the current animation is not running.
Therefore preventing the animation perpetually gaining a delay if moving the mouse over thumbnails fast enough.
BUG: 245091