not set unexisting attribute

theano/sandbox/test_multinomial.py

@@ -18,7 +18,7 @@ def get_mode(gpu):
                               'local_gpu_multinomial')
     if isinstance(mode.linker, theano.gof.PerformLinker):
         mode.linker = predefined_linkers['c|py']
-    if not getattr(mode.linker, 'c_thunks', True):
+    if hasattr(mode.linker, 'c_thunks'):
         mode.linker.c_thunks = True
     return mode