Blender Git Loki

MeshCache: add error handling to `fread()` calls

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