Fix iCCP: known incorrect sRGB profile warnings in stderr

I processed all images through `convert -strip`.
Changed the error report so it brings the user to Github directly

(Cherry-picked from the qt5 branch, with conflicts...)

Making error reporting too easy results in too much context-less
tracebacks which demand attention and, in the end, aren't of much use.

Requiring the user to report errors on Github will reduce the number of
reports, but hopefully make these reports have better context.

Conflicts:
	error_report_dialog.py