Fix update execute while app exit

[jiangheng90]

Objective

Fixes #17533 #16066

update execute while app is exit, if we query object in update, it will cause panic becuse these object has been recycle

this problem is caused from #14155, by fix App hanging in example window_settings. when windows all destroyed to be zero the all_invisible will be true, then cause update execute after app exit.

Solution

before update check app state is exit. if exit no execute.

another choice is to see the number of windows if it goes to zero, just make all_invisible to be false

but I think check app state is more reliable, because maybe in some case we need app to run background with no window.

for now, I just check if app is exit.

[mockersf]

we want to be able to run update when the app is exiting, so this is not a good fix