Why set res->error to zero for log function in handle_math_d_long of handleReal.cpp?

[yixin-09]

I don't know why set res->error as zero when temp < 0 for log and log10 function:

res->error = temp - computedResd;
if(opCode == LOG || opCode == LOG10){
if(temp <= 0){
res->error = 0;
}
}
in lines 1169-1174 of handleReal.cpp.
The code will ignore errors when inputs close to 1, for example, x = 0.99999 and temp = Log(x).