Fix autoretract bug

After some commits (https://github.com/ErikZalm/Marlin/commit/3c927901a4dcc4fb4bbfd6bf914a35f8277165db ; https://github.com/ErikZalm/Marlin/commit/9db9842aeabe76f78bfda67fac89b75a531bb0b7) the firmware retraction was broken. This pull request fixes it