Editor crahes when changing variable.

Hi, I am having problems changing a variable, either global or local. Can you help me, please ? So, I read from a string and if it’s a number, I continue reading until I get the full number, then I send the number to other function which does something and then it calls the function again to read next number. I need to clear nrs, because I use nrs.Len in switch.

functionA(){
… if(isnumber){
FString nrs="";
nrs+=Parsed[ni].Mid(nj,1);
++nj;
UE_LOG(LogTemp, Warning, TEXT("%s"), *nrs.Mid(0,1));

while(Parsed[ni].Mid(nj,1).Equals(" “)==false && nj!=Len){
nrs+=Parsed[ni].Mid(nj,1);
UE_LOG(LogTemp, Warning, TEXT(”%s"), *nrs.Mid(it,1));
++nj;
}
++nj;
UE_LOG(LogTemp, Warning, TEXT("%d"), nrs.Len());

nrslen=nrs.Len();
UE_LOG(LogTemp, Warning, TEXT("%d"), nrslen);

switch(nrslen){
case 0: break;
case 1: functionB(nrs.Mid(1,1));
break;
case 2:functionB2(nrs.Mid(1,1),nrs.Mid(2,1));
break;
default: break;
}
}
}

functionB(nrs){
print(nrs);
functionA();
}