Remove useless condition

theano/scalar/basic.py

@@ -4004,8 +4004,7 @@ class Composite(ScalarOp):
         self.__dict__.update(d)
         # We must call init to set fgraph and _impls again, as otherwise
         # self.perform will not work.
-        if not hasattr(self, "prepare_node_called"):
-            self.prepare_node_called = set()
+        self.prepare_node_called = set()
         self.init_fgraph()
         self.init_py_impls()
         assert self._c_code