fix(menuable): added comparison logic for shown
fix(menuable): added comparison logic for shown

fixed a bug where the **isShown** method in the `menuable` mixin would error when trying to check
the display of an element that had already been destroyed

Webifi/vuetify,azaars/vuetify,Phlow2001/vuetify,Webifi/vuetify,KaelWD/vuetify,vuetifyjs/vuetify,Phlow2001/vuetify,Webifi/vuetify,Phlow2001/vuetify,vuetifyjs/vuetify,azaars/vuetify,vuetifyjs/vuetify,KaelWD/vuetify,vuetifyjs/vuetify,Phlow2001/vuetify,KaelWD/vuetify