1-1 Needs better UI for when camera numbers clash

[manukautech]

I set up an outdoor camera trial tonight (18 Jan 2019). Then went home and ran the app on my desktop to monitor progress. However I also did a camera test using the desktop webcam and I selected camera number 1 same as the field camera selection. Then no more images coming from the field camera.
TODO go back tomorrow and restart the field camera.
TODO communicate and lock camera numbers when they are in use so that users can only start new cameras on vacant numbers. I thought I had done that but obviously it needs more attention.

[manukautech]

I thought this was a crash.
Further testing shows that there are 2 issues here.
This issue - needs better UI feedback when the user selects a camera number that is already in use.
Fork "Ver.0.8.2 Cam Numbers" implements this. It is testing well on a Windows 10 laptop and a Windows 10 desktop with webcam.
New issue - serious - all trials with Firefox-on-Android are now crashing after running 5 to 15 min. I am starting a new issue for this. Extensive testing including rolling back to earlier versions is making no difference. I do know that the last successful long run field trial of this configuration was 05 Jan 2019. The next field trial which crashed was 18 Jan 2019. I can find nothing wrong yet with the code. There was a new version of Firefox on 09 Jan 2019 in between these dates so I need to include in my detective work the possibility that something has happened to a Firefox system function. The main candidate for investigation is:
navigator.mediaDevices.getUserMedia(constraints)

[manukautech]

The FireFox crash is a separate issue. That is now accepted by the Mozilla Foundation as a FireFox bug and is under investigation there. Ref:
https://bugzilla.mozilla.org/show_bug.cgi?id=1521760

[manukautech]

When a a Camera Channel is already in use, version 0.9.0 just published 30 Mar 2019 gives a warning with an option to "Takeover"