box: frommap() bug fix

- If an optional argument is provided for
  space_object:frommap() (which is {table = true|false}),
  type match for first arguments is omitted, which is
  incorrect. We should return the result only after making
  sure it is possible to build a tuple.

- If there is a type mismatch, however, frommap() does not
  return nil, err as it is mentioned in the description, so we
  change it to be this way.

Closes #4262