Prevent None paths from breaking code in get_url.

[ndesamuelmbah]

Added code to prevent None string values in Path from breaking code when getting urls of storage paths.
Also ensured that we are removing all trailing "/" characters from paths when necessary by converting path = path[1:] to path = path.lstrip('/')

[ndesamuelmbah]

Hello Folks,
I ran into some problems with None string values being set to the value of path in storage class and the trying to apply startswith on the path value. I thought it would be better to have it fixed in the package than to have me fix it only for myself.

[arham-sayyed]

awsome fix!

Was stuck on this problem for literal 2 days! thankyou very much for this fix.
Your PR must be merged soon!

Thanks a lot Again!