Bug in firmwareupdate using Attiny1606_27C400_Programmer

Programming a Attiny1606_27C400_Programmer firmware results in a strange error after step 5:

It shows "OK" and continues in step 7, which breaks with an "Wrong answer from bootloader:" answer

looking in the code I found, that line 273 checks for

if appstart > 0:

which is contradictional to the boot-code update-check in the main routine

Changing line 273 to

if appstart == 0:

solved the problem