iStochastic - array out of range

Hi Experts,

I use iStochastic function to check Main and Signal values and do something with them.

but when i call the array, the error <array out of range> shown in the journal section.

the code is here:

int stoHandle;
double mainLin[];
double sigLin[];

ArraySetAsSeries(mainLin,true);
ArraySetAsSeries(sigLin,true);

stoHandle=iStochastic(_Symbol,_Period,21,3,3,MODE_SMA,STO_LOWHIGH);
CopyBuffer(stoHandle,0,0,3,mainLin);
CopyBuffer(stoHandle,1,0,3,sigLin);

Print(mainLin[0], " : " , sigLin[0]);

I did this with many indicators like iADX, iMA, etc...

Only iStochastic Shows (array out of range)

any help will be appreciated