Don't precompute stuff if it isn't used.

theano/compile/debugmode.py

@@ -1109,6 +1109,9 @@ def _get_preallocated_maps(node, thunk, prealloc_modes, def_val,
     # is less relevant.
     # Dimensions should be align by the innermost index, so we iterate
     # from the end of shapes.
+    if ('strided' in prealloc_modes or
+        'wrong_size' in prealloc_modes or
+        'ALL' in prealloc_modes):
         max_ndim = 0
         rev_out_broadcastable = []
         for r in considered_outputs: