gh-145376: Fix null pointer deref in md5module.c

Modules/md5module.c

@@ -87,7 +87,9 @@ static void
 MD5_dealloc(PyObject *op)
 {
     MD5object *ptr = _MD5object_CAST(op);
-    Hacl_Hash_MD5_free(ptr->hash_state);
+    if (ptr->hash_state != NULL) {
+        Hacl_Hash_MD5_free(ptr->hash_state);
+    }
     PyTypeObject *tp = Py_TYPE(op);
     PyObject_GC_UnTrack(ptr);
     PyObject_GC_Del(ptr);