Personal merge request view (merge_requests?assignee_id) should also show authored unassigned MRs

Description

I have opened gitlab-ce!7207 but it has not been assigned to me (or anyone). It is rather unintuitive that this MR is not shown in my personal merge request view (/merge_requests?assignee_id=<my userid>) reachable from the sidebar on the left as "Merge Requests".

Merge Requests that have been opened by me but not assigned are definitely "mine" in my mind, generally require attention from me, and I'd guess most other users feel the same.

Proposal

The personal merge request view should also include unassigned MRs that are authored by the user.