WIP: avoid the error when comparing numbers with reference
As reported in ATR-21066, if ref_v is 'n/a', format code for int in L.265 does not work for str. Is it OK to put -1 instead of 'n/a' in L.133? Or, if this str('n/a') plays an important role in the other places, please fix it appropriately. Tagging @rafal @stelzer @ssnyder who updated this script recently.