message: Fix cprop transfer function
diff: @@ -127,8 +127,7 @@ def cprop_merge(vals_list):
  for vals in vals_list:
  for name, val in vals.items():
  if val == '?':
  - if name not in out_vals:
  - out_vals[name] = val
  + out_vals[name] = '?'
  else:
  if name in out_vals:
  if out_vals[name] != val:
  