fix error returned.

theano/ifelse.py

@@ -340,7 +340,7 @@ def ifelse(condition, then_branch, else_branch, name=None):
 
             if then_branch_elem.type != else_branch_elem.type:
                 # If the types still don't match, there is a problem.
-                raise ValueError(
+                raise TypeError(
                         'The two branches should have identical types, but '
                         'they are %s and %s respectively. This error could be '
                         'raised if for example you provided a one element '