make sure malloc didn't return nil

common/os_calls.c

@@ -84,9 +84,12 @@ g_malloc(int size, int zero)
 
   rv = (char*)malloc(size);
   if (zero)
+  {
+    if (rv != 0)
     {
       memset(rv, 0, size);
     }
+  }
   return rv;
 }