Tool fails if server returns 200 OK on empty responses

[Zeroji]

I've used GWTMap on a server that returns a 200 for files that don't exist, such as */0.cache.js. It breaks with the error error: target resource seems invalid...

I fixed it locally by changing this line https://github.com/FSecureLABS/GWTMap/blob/5624f7440acc41dc2051d8d83bc56cfbd12bca45/gwtmap.py#L891 to

    if not response:
        miss += 1
    elif status == 200: