Solution

Some X++ modifications are needed in two Forms.

Form EventCreateRule, method modified on Field EventRule.UserId:

public void modified()
{
  super();

  // BEGIN
  eventRule_SendEmailAddress.text(
        SysUserInfo::find(EventRule.UserId).Email);
  // END
}

Form EventRule, method setControlsActive on DataSource EventRule:

...
else if (!canShowPopUpCheckBox)
{
  alertMeBy.visible(true);
  eventRule_ShowPopUp.visible(false);
  eventRule_SendEmail.visible(true);
  eventRule_SendEmailAddress.visible(true);
  // BEGIN
  //eventRule_SendEmailAddress.text(userInfo.Email);
  eventRule_SendEmailAddress.text(
    SysUserInfo::find(EventRule.UserId).Email);
  // END
}
else
{
  alertMeBy.visible(true);
  eventRule_ShowPopUp.visible(true);
  eventRule_SendEmail.visible(true);
  eventRule_SendEmailAddress.visible(true);
  // BEGIN
  //eventRule_SendEmailAddress.text(userInfo.Email);
  eventRule_SendEmailAddress.text(
    SysUserInfo::find(EventRule.UserId).Email);
  // END
}

if (eventRule.UserId == curuserid())
  eventInboxSingleton.enabled(true);
...

Solution

To make your find method work, you need to pass through the reference to the temporary table.

public static TmpAvgCubicMeterPrices find(
         ProjId                    _projId,
         InventDimCombinationName  _inventDimCombinationName,
         TmpAvgCubicMeterPrices    _tmpAvgCubicMeterPrices,
         boolean                   _forUpdate = false)
{ 
    TmpAvgCubicMeterPrices   tmpAvgCubicMeterPrices; 
    ; 

    tmpAvgCubicMeterPrices.setTmpData( 
              _tmpAvgCubicMeterPrices);

    tmpAvgCubicMeterPrices.selectForUpdate(_forUpdate);

    select firstonly tmpAvgCubicMeterPrices
       where tmpAvgCubicMeterPrices.ProjId
                                                   == _projId  
       && tmpAvgCubicMeterPrices.InventDimCombinationName
                                == _inventDimCombinationName; 


    return tmpAvgCubicMeterPrices; 
}