fixed a case for search_assignable_users_for_issues where username an…

[niteshthakur]

This change fixes an issue where username and query arguments are not passed for method search_assignable_users_for_issues

[niteshthakur]

need to remove check if not username and not query:

[studioj]

looks legit , could you add a test which validates this?

[adehad]

need to remove check if not username and not query:

We still need this, this is what provides a useful error message to the user.

Technically this is also fixed by the changes in: #1394 - where this check is moved to before the arguments are used

[adehad]

Closing as #1394 is now merged.

@niteshthakur if you still have this problem do let me know and we can reopen this PR or create a new PR to address this