cannot convert nothing to group

[Nina]

Hello, this is my code and I just can't seem to find what's causing this error: cannot convert nothing to group.

scope Warmth initializer Init
    globals
        private constant integer WarmthRatio = 5
        private constant integer WarmthBuff = 'B000'
    endglobals

    function HasBuff takes nothing returns boolean
        return ( GetUnitAbilityLevel(GetEnumUnit(), WarmthBuff) > 0)
    endfunction

    function SetDwarfWarmth takes nothing returns nothing
        if (HasBuff()) then
            set udg_Warmth[GetPlayerId(GetOwningPlayer(GetEnumUnit()))] = ( udg_Warmth[GetPlayerId(GetOwningPlayer(GetEnumUnit()))] + WarmthRatio )
        endif
    endfunction

    function Trig_Warmth_Actions takes nothing returns nothing
    local group g = CreateGroup()
    call ForGroup( GroupEnumUnitsInRect(g,bj_mapInitialPlayableArea,Filter(function True)), function SetDwarfWarmth )
    call DestroyGroup(g)
    endfunction

    //===========================================================================
    function Init takes nothing returns nothing
        local trigger t = CreateTrigger(  )
        call TriggerRegisterTimerEvent( t, 2, true )
        call TriggerAddAction( t, function Trig_Warmth_Actions )
    endfunction
endscope

 

[Uberplayer]

That's because GroupEnumUnitsInRect function does not return you a group. It returns nothing.

function Trig_Warmth_Actions takes nothing returns nothing
    local group g = CreateGroup()
    call GroupEnumUnitsInRect(g, bj_mapInitialPlayableArea, Filter(function True))
    call ForGroup(g, function SetDwarfWarmth)
    call DestroyGroup(g)
    set g = null //Has to be cleaned
endfunction

 

[Nina]

Oh I see how did I miss that and I also didn't know I had to null groups after destroying them, think you could explain that? Because if it's destroyed it's not there so how can you null null?

 

[Expelliarmus]

Maybe this will help?

 

[Nina]

Thanks I get it now