Add specific error message for if a file is invalid

[vrad-exe]

Describe Your Suggestion

Currently if you attempt to open a file which is invalid or not a supported file type, it will tell you to make sure the file isn't in use by another program even though that's not the issue and won't actually help anything. The failure is happening at 2 distinct places here (opening the file vs. reading its contents), so there should be a unique error message for the latter that explains that the file may be corrupt or an unsupported format which happens to share the same extension.