Ticket #48149 - ns-slapd double free or corruption crash
    
    Description: coverity defect: 2. Defect type: FORWARD_NULL
    If mempstat is issued while an online import is running, it'd crash
    the server.
    
    https://fedorahosted.org/389/ticket/48149
    
    Reviewed by rmeggins@redhat.com (Thank you, Rich!!)
    
    (cherry picked from commit 608fcdfcd792e351edfc12cf89c2c9c6fc2a56d0)