If you don't have your account linked, and you press F6 many times, then try to cancel, you have to press cancel multiple times in order to exit the menu.
For instance, go in game and press F6 10 times in a row. When the "Twitch Broadcasting Unavailable" menu pops up, press cancel. You have to press the "Cancel" button 11 times before it exits.
Linked issues
is duplicated by 5
MC-42537
Minecraft - twitch broadcasting unavailable, you must double click cancel button to exit this (my english is bad :-( )
Resolved
MC-49332
'Twitch Broadcasting Unavailable' messages sum up after repeatedly hitting F6
Resolved
MC-50317
Multiple Twitch Overlays Ontop of eachother
Resolved
MC-61010
Twitch account linking
Resolved
MC-77158
First click on "Cancel" in error message for streaming does nothing (DOUBLON)
Resolved
Confirmed.