The same dock icon problem occurred with another app, and the author suggested:
macOS will eventually remove services from apps that are no longer installed. You may be able to do it quicker by entering this Terminal command:
/System/Library/CoreServices/pbs -flush
... which worked after reboot.
macOS will eventually remove services from apps that are no longer installed. You may be able to do it quicker by entering this Terminal command:
/System/Library/CoreServices/pbs -flush
... which worked after reboot.