Custom HamburgerButton not working in v9

[kgeipel-retail7]

The Hamburger Button is not working at all in v9.
After a research, it seems that this Else branch is missing completely in v9.8.0/pkg/ui/shell (also in all previous versions):
https://github.com/maxence-charriere/go-app/blob/v10.0.4/pkg/ui/shell.go#L210

Would be nice if that could be fixed within the v9 release, because I don't want to upgrade to v10 at the moment.