[Fix] Allow for url to be an optional part of the patches entry

[sour-dani]

Although the url entry in versions.json is technically optional, in practice beans-rs still expects there to be a url entry for each patch version.

I would like for this to be changed in code to reflect the intended functionality.

[ktwrd]

Thanks for pointing this out! I just checked the Bullseye/Kachemak v1 schema in Cockatoo and the url property is optional.

BlueboxTeam/Cockatoo/Adastral.Cockatoo.DataAccess/Models/Bullseye/BullseyeV1.cs (line 59)