Handle return value of `fread()`, by showing an error message when the
file cannot be read from and stopping further processing. Not only is
error handing a good idea, it also prevents GCC from warning that the
return value of `fread()` should not be ignored.
This is similar to {D9916}.
Reviewed By: campbellbarton
Differential Revision: https://developer.blender.org/D10079