[UI] Image Set Native Size then Unity not responding

hi all,
i'm new to unity and i've been playing with unity UI , button, scroll rect, canvas, and such.
now i'm making my App (yes, App, not a game).
start this project about a week ago, find no errors whatsoever, but now i'm facing an issue.

my unity goes not responding, whenever i 'set native size' for my image.
tried to close unity, open it again, did that a few times, but it keep crashing.

anyone know why is this happening?