fix: Handle syntax errors in required file

[shadmansaleh]

If the required file has syntax errors then loadfile will return nil, error. That nil is directly passed to string.dump which throws a nil error and the syntax error is lost.

This adds a check so that doesn't happen

A simple way test is to have a file with a syntax error like

print("hello"

And try to require it.

@lewis6991 this is the issue that I mentioned earlier in matrix.

[lewis6991]

Thanks