In case a stored procedure is invoked in PS mode with argument of type ROW()
like the following one:
  CALL p1(ROW(10,20))
such statement fails with the error
  ER_OPERAND_COLUMNS (1241): Operand should contain 1 column(s)

The reason of emitting the error is that wrong method was invoked
on fixing an item corresponding to an argument of stored procedure -
the method fix_fields_if_needed_for_scalar() was called instead of
fix_fields_if_needed() that should be called.