Bug 613056 - fix coverify Defect Type: Null pointer dereferences issues 11892 - 11939

https://bugzilla.redhat.com/show_bug.cgi?id=613056
Resolves: bug 613056
Bug description: Fix coverify Defect Type: Null pointer dereferences issues 11892 - 11939
description: Catch possible NULL pointer in slapi_free_search_results_internal().

ldap/servers/slapd/plugin_internal_op.c

@@ -464,6 +464,11 @@ slapi_free_search_results_internal(Slapi_PBlock *pb)
 {
     int i;
 	
+    if(pb == NULL)
+    {
+        return;
+    }
+
     if(pb->pb_plugin_internal_search_op_entries != NULL)
     {
         for(i=0; pb->pb_plugin_internal_search_op_entries[i] != NULL; i++)