[Cin] fileexr reading error handling

[Andrea paz]

> Thanks! Did you try yesterday's scenario with bg render set to jpeg, enabled, then set to any other compression / filetype, and re-enabled via menu so you have red bar at top of topmost video track but at this point it made from wrong image type so prev. version of file reading routines were crashing? if you position playhead there?

I don't quite understand the problem.
1- No crash, but I don't know if I've done the steps you described correctly.
2- Creating a BRender in jpg, then disabling the BG. Going into
Preference and changing the BR from jpg sequence to EXR (and PNG)
sequence, creating a new BRender, I still have the jpeg sequence
active and no sequences were created with the other formats.
3- Closed and restarted CinGG; created new BRender in tga: all OK.