add defensive checks to PyTraceMalloc_Untrack

Author: kumaraditya303

Python/tracemalloc.c

@@ -1236,6 +1236,12 @@ PyTraceMalloc_Untrack(unsigned int domain, uintptr_t ptr)
     }
 
     TABLES_LOCK();
+    // Check again now that we hold the lock
+    if (!tracemalloc_config.tracing) {
+        TABLES_UNLOCK();
+        /* tracemalloc is not tracing: do nothing */
+        return -2;
+    }
     tracemalloc_remove_trace_unlocked(domain, ptr);
     TABLES_UNLOCK();
     return 0;