If getattr() fails, hasattr() will fail as well.

Removed hasattr() check, because hasattr() will call getattr() internally
anyway. If hasattr() fails, it means that getattr() has failed. So, there is no
need to call hasattr() before getattr().

src/c/bison_callback.c

@@ -104,14 +104,11 @@ PyObject* py_callback(PyObject *parser, char *target, int option, int nargs,
     if (unlikely(!res)) return res;
 
     // Check if the "hook_handler" callback exists
-    if (unlikely(!PyObject_HasAttr(parser, py_attr_hook_handler_name)))
-        return res;
-
     handle = PyObject_GetAttr(parser, py_attr_hook_handler_name);
 
-    if (unlikely(!handle)) {
-        Py_DECREF(res);
-        return NULL;
+    if (!handle) {
+        PyErr_Clear();
+        return res;
     }
 
     // Call the "hook_handler" callback