layers: Check for NULL ptrs while iterating over fenceMap
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index 8394bc8..3dc0412 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -250,7 +250,7 @@
     map<uint64_t, MT_FENCE_INFO*>::iterator it = fenceMap.begin();
     map<uint64_t, MT_FENCE_INFO*>::iterator temp;
     while (it != fenceMap.end()) {
-        if (((*it).second)->queue == queue) {
+        if ((((*it).second) != NULL) && ((*it).second)->queue == queue) {
             temp = it;
             ++temp;
             deleteFenceInfo((*it).first);