SoftPwm: fix assertion failure
SoftPwm: fix assertion failure

ambrop72/aprinter,fixator/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,ambrop72/aprinter,johnkingsley/aprinter,fixator/aprinter,ambrop72/aprinter,fixator/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,fixator/aprinter,ambrop72/aprinter,johnkingsley/aprinter,ambrop72/aprinter,fixator/aprinter,fixator/aprinter,ambrop72/aprinter,johnkingsley/aprinter,ambrop72/aprinter