[Cin] fileexr reading error handling

[Andrea paz]

I tried leaving the BR on and also turning it off between trials (from
"Preferences" not "toggle"). I have tried disabling the BR and then
deleting the sequence manually. In this case, when I try a new
sequence in a different format I get a series of errors that it does
not find the previous jpg images and does not do the BR. Only by
restarting CinGG does the BR with new file types work again.
I will try more tests later trying to cause a crash. Question: is it
important to use "try ffpeg last/first"? Should I try both or should I
just use "last"?