SC2Mapster

This one works but gives the error.

transfer kills
    Events
        Unit - Any Unit dies
    Local Variables
        Killing_Hero = Hero_Array[(Owner of (Triggering unit))] <Unit>
        Hero_Current_Kills = (Killing_Hero Kills (Current)) <Real>
        Grenade_Kill_Count = ((Triggering unit) Kills (Current)) <Real>
    Conditions
        (Unit type of (Triggering unit)) == Grenade 1
    Actions
        UI - Display (Combine ("You Recieved ", (Text(Grenade_Kill_Count) with Any Precision decimal places), " kills!")) for (All players) to Subtitle area
        Unit - Set Killing_Hero Kills to (Hero_Current_Kills + Grenade_Kill_Count)

This one works perfectly, but is less beautiful. Plus I just want to know why I would get an error.

transfer kills 2
    Events
        Unit - Any Unit dies
    Local Variables
        Killing_Hero = No Unit <Unit>
        Hero_Current_Kills = 0.0 <Real>
        Grenade_Kill_Count = ((Triggering unit) Kills (Current)) <Real>
    Conditions
        (Unit type of (Triggering unit)) == Grenade 1
    Actions
        Variable - Set Killing_Hero = Hero_Array[(Owner of (Triggering unit))]
        Variable - Set Hero_Current_Kills = (Killing_Hero Kills (Current))
        UI - Display (Combine ("You Recieved ", (Text(Grenade_Kill_Count) with Any Precision decimal places), " kills!")) for (All players) to Subtitle area
        Unit - Set Killing_Hero Kills to (Hero_Current_Kills + Grenade_Kill_Count)

Is it because I referenced Killing_Hero when setting up the variable Hero Current Kills? Both triggers do the job but the first trigger does it while also issuing an warning.

It's because in the script, variable declarations come BEFORE the conditions are checked.  I c/ped this from my own script:

//--------------------------------------------------------------------------------------------------
// Trigger: Cancel
//--------------------------------------------------------------------------------------------------
bool gt_Cancel_Func (bool testConds, bool runActions) {
    // Variable Declarations
    int lv_jumpAbility;

    // Variable Initialization
    lv_jumpAbility = 0;

    // Conditions
    if (testConds) {
        if (!((gv_engine_dialogUp == false))) {
            return false;
        }

        if (!((gv_aITurnUp == false))) {
            return false;
        }

So what's happening in your first trigger is that:
         Killing_Hero = Hero_Array[(Owner of (Triggering unit))] <Unit>
is being initialized for EVERY dying unit, and the dying unit is causing an index that's out of bounds for the Hero_Array.  You can fix this by increasing the size of the Hero_Array to account for all possible values for Owner of (Triggering Unit), which should be 16.

@xenrathe: Go

Thanks for the help. Is there a reason why they have the variables before the conditions?

@KelvCM: Go

I'm sure there's a compile reason, but I couldn't say.