Storage API: add safety check for cases when there is no storage used.

src/flow-storage.c

@@ -52,6 +52,7 @@ void FlowFreeStorageById(Flow *f, int id) {
 }
 
 void FlowFreeStorage(Flow *f) {
+    if (FlowStorageSize() > 0)
         StorageFreeAll((Storage *)((void *)f + sizeof(Flow)), STORAGE_FLOW);
 }
 

src/host-storage.c

@@ -48,6 +48,7 @@ void HostFreeStorageById(Host *h, int id) {
 }
 
 void HostFreeStorage(Host *h) {
+    if (HostStorageSize() > 0)
         StorageFreeAll((Storage *)((void *)h + sizeof(Host)), STORAGE_HOST);
 }