Gnome version 44.1 / Dash-to-Dock v81
Extension fails to launch and outputs the above error message. Also when the Gnome desktop starts, the 'Dash-to-Dock' settings popover is active. Disabling Dash-to-Dock resolves the issue.
Might be an issue in the latest version of Dash-to-Dock failing to return a _menu property.
Workaround: comment out lines 1910 - 1917 in extension.js. This gets things working again.