try to fix calibration error in first start

[avouspierre]

fix #92 (hope)

[bjornoleh]

Did you find a good way to reproduce the bug in the first place? I am unsure if my initial observations of cause and effect were accurate. If we know how to reproduce accurately, I can test again before and after this fix.

[avouspierre]

Not sure but I succeeded to reproduce once...

[bjornoleh]

I can not reproduce this any more without your fix... But your changes look reasonable, and I suppose it will be best to merge this into alpha now, and if no more crash reports, we suppose this was effective?

I did build with the change of this PR, and it caused no immediate issues.

I will merge this now so that the change becomes available (it is currently in your private branch only).

Please remember to make a separate PR to dev after some time of testing in alpha (after submodules are brought into dev).