Thanks for the explanation. I got it 
Let me elaborate my use case:
I anyway have a bridge in my LAN and this Tor Browser instance is mainly used for accessing geoblocked content behind heavy Google captchas hence there are some modifications to it’s torrc (only two countries for exiting and a modified MaxCircuitDirtiness) to make it work at all.
Avoiding censorship of Tor is not a concern in this setup but by using my own bridge i automatically test if it still works, i avoid a useless roundtrip through the internet and i get a reliable “guard” with enough guaranteed bandwidth for video streaming.
Not having the circuit display is inconvenient for me because i can not check anymore in what country i am exiting right now and i have to use the keyboard for requesting a new circuit.
Having to switch between mouse and keyboard a few times for a good circuit gets more inconvenient the longer you were already confronted with useless captchas. 
I guess my bug report has just become a feature request:
“Please make it possible to request a new circuit with the mouse when there is no circuit window (or fix the circuit window in all cases)”
I fixed the situation for me by looking up my bridge fingerprint and the circuit display works again.
But instead of quickly typing my bridge LAN IP i now have to copy everything over from a textfile. 