CiviMember Renewal - add error trap for misconfigured status rules

Currently the method CRM_Member_BAO_MembershipStatus::getMembershipStatusByDate returns without an empty status ID if the site's membership status rules are configured such that some membership start / end date conditions are not covered. This then causes fatal errors trying to insert a membership_log record and / or update the membership status.

Need to add error checking to the method so it returns a clear error message if we can't find a valid status for the membership.