Merge branch '346-some-cameras-can-t-focus-on-qr-codes' into 'master'

Set focus mode properly when scanning QR codes

This simple fix contributed by @m8r-v9bo74 fixed the issue on my Xperia
Pro that could never focus on the QR code before. Focusing and scanning
still works on my other test devices.

Closes #346

See merge request !243