In #12607 we removed the restriction that prevented a user from having zero dashboards. This was to support an automation use case to replace the first dashboard of a user w/ another layout. This is not an ideal fix and can lead to buggy UX if used incorrectly (ie, not adding a dashboard after removing all of them).
This potential inconsistency should be solved in some way. The actual solution is yet to be determined, but must not break mobile.