Unexpected owner reassignment when editing resource with no current owner

[zerocrates]

Resource forms have an "Owner" dropdown in the Advanced tab, to change the current owner of the resource. The select here doesn't include a blank "Select below" option, nor a "no owner" option, so when you load the edit form for a resource that has no owner, whichever user is first in the select dropdown list will be preselected. Saving the form will result in changing the ownership of the resource to that user, even if the user never altered the setting or even opened the Advanced tab.

Fixing this probably means putting in a "no user" option when the resource currently has no user, so the default is to not make any change. I'm thinking we don't want to just make "no owner" an option you can always choose but we could do that as well.