[Fix/Enhancement] URI Sanity Check

Hello,

When using the Pritunl Client and the option to import profiles using the URI, the input allows for an invalid url.

Specifically, causing an issue with some clumsy copy+pasters, is it allows a URI that starts with " " aka %20. Doing so also changes the “port” to 443 instead of the actual port (not that it would ever connect, but it’s still odd).

pritunl://vpn.example.com:5056/ku/X4xKFNTZ

While troubleshooting an import, I noticed in the log:
[2024-7-23 11:20:34][ERROR] Request: Client error ssl=true hostname=%20pritunl port=443 method=GET path=//vpn.example.com:5056/ku/X4xKFNTZ ttl=12000

As a domain should never start with a space, I believe a sanity check should be added to prevent the invalid entry with an error prior to pressing import or prior to closing the import window.