[Cin] fileexr reading error handling

[Andrea paz]

I did some more testing for BR.
I noticed that to change the image type you just remove the "toggle"
and then from "Preferences" change format and give "Apply" (sometimes
you need "OK"). Almost always it works that way; at the limit you have
to diasbilitate BG, give "apply" then reactivate BG and give "apply."
At this point on the timeline you reapply the "Toggle" and get the
rendering in the new format.
I tried applying various filters and changing formats with those
filters. I tried playback and reverse playback. I never had any
crashes.