this problem should occure while u r phased away from your tank
try this (check the spelling first, typed from mind, no VS support atm^^)
maybe u can /should check if you're in the same phase than your tank.
if this is not possible, then do a workaround like CanCast("DivineLight",tank) (check if u can cast this to the tank, if not, then don't try to target something)
	
	
	
		PHP:
	
	
		        public static bool Halt()
        {
if(tank!=null && tank.isValid && !tank.Dead && !tank.Ghost){
            if (tank.CurrentTarget != null && Me.CurrentTarget == null)
                tank.CurrentTarget.Target();
}
            if (StyxWoW.GlobalCooldown || Stop_SET || Me.Mounted || Helpers.ImEatingOrDrinking())
                return true;
            return false;
        }
	 
 
or try this if there's no way to check the tank in this case
	
	
	
		PHP:
	
	
		        public static bool Halt()
        {
try{
            if (tank.CurrentTarget != null && Me.CurrentTarget == null)
                tank.CurrentTarget.Target();
}
catch(Exception ex)
{
Logging.Write("Error occured while targetting enemy: {0}",ex.toString());
}
            if (StyxWoW.GlobalCooldown || Stop_SET || Me.Mounted || Helpers.ImEatingOrDrinking())
                return true;
            return false;
        }
	 
 the try'n catch block should prevent HB from stopping the healing
damn, while checking your svn, i saw some old dispelling code for HPaly ... if u want to use this for more (druid,priests, shamans) u have to tweak the code for druids, cause not every Restoration Druid can dispel Disrupting Shadows (this was a hard school when i was trying to dispel this)
i'm sure the dispelling could be rewritten and could be done much shorter (i'll take a look) cause ... i hate these stupid for each loops, they're unnecessary 
