Fix gradient disabler optimization in CTC CPU Op to avoid modifying the node inplace

theano/tensor/nnet/ctc.py

@@ -168,5 +168,5 @@ def local_ctc_no_grad(node):
     if isinstance(node.op, ConnectionistTemporalClassification):
         if len(node.outputs) > 1:
             if len(node.outputs[1].clients) == 0:   # gradient is not used
-                node.op = ConnectionistTemporalClassification(compute_grad=False)
-                node.outputs = node.outputs[:1]   # costs only
+                node.op.compute_grad = False
+                return [ConnectionistTemporalClassification(compute_grad=False)(*node.inputs)]