message: Fix fold bug.
diff: @@ -160,7 +160,7 @@ def lvn_block(block, lookup, canonicalize, fold):
  if val:
  # Is this value foldable to a constant?
  const = fold(num2const, val)
  - if const:
  + if const != None:
  num2const[newnum] = const
  instr.update({
  'op': 'const',
  