CRM-13816 - Undefined index notice due to disabled memberships in CRM_Member_BAO_Membership::updateAllMembershipStatus()

http://issues.civicrm.org/jira/browse/CRM-13816
Merge pull request #2073 from dlobo/CRM-13816

CRM-13816 - Undefined index notice due to disabled memberships in CRM_Member_BAO_Membership::updateAllMembershipStatus()