This is code from # Kernel/Modules/AgentTicketActionCommon.pm line 429...
# check time units, but only if the current screen has a note
            # (accounted time can only be stored if and article is generated)
            if (
                $Self->{ConfigObject}->Get('Ticket::Frontend::NeedAccountedTime')
                && $Self->{Config}->{Note}
                && $GetParam{TimeUnits} eq ''
                )
            {
                $Error{'TimeUnitsInvalid'} = ' ServerError';
            }
        }

I fix code like this...
  # check time units
        if (
            $Self->{ConfigObject}->Get('Ticket::Frontend::AccountTime')
            && $Self->{ConfigObject}->Get('Ticket::Frontend::NeedAccountedTime')
            && $GetParam{TimeUnits} eq ''
            && $Self->{Config}->{Note} 
            )
        {
            $Error{'TimeUnitsInvalid'} = ' ServerError';
        }
And think it will be well. If you have any suggestion, please tell me.
Regards
Zoran