fixed a bug

theano/tensor/opt.py

@@ -1605,6 +1605,7 @@ def local_useless_elemwise(node):
 
             if isinstance(node.inputs[0], T.TensorConstant):
                 const_val = T.extract_constant(node.inputs[0])
+                if not isinstance(const_val, Variable):
                     if const_val == 0:
                         return zeros_like(node, 1)
                     else:
@@ -1612,6 +1613,7 @@ def local_useless_elemwise(node):
 
             if isinstance(node.inputs[1], T.TensorConstant):
                 const_val = T.extract_constant(node.inputs[1])
+                if not isinstance(const_val, Variable):
                     if const_val == 0:
                         return zeros_like(node, 0)
                     else:
@@ -1622,6 +1624,7 @@ def local_useless_elemwise(node):
 
             if isinstance(node.inputs[0], T.TensorConstant):
                 const_val = T.extract_constant(node.inputs[0])
+                if not isinstance(const_val, Variable):
                     if const_val == 0:
                         return [node.inputs[1]]
                     else:
@@ -1629,6 +1632,7 @@ def local_useless_elemwise(node):
 
             if isinstance(node.inputs[1], T.TensorConstant):
                 const_val = T.extract_constant(node.inputs[1])
+                if not isinstance(const_val, Variable):
                     if const_val == 0:
                         return [node.inputs[0]]
                     else: