Gname-shell crash "quickly" enabling/disabling the extension

[micheleg]

Enabling and disabling the extension repeatedly (three times in three seconds is enough) via gnome-tweak-tool makes the shell crash.

(gnome-shell:14118): Clutter-WARNING **: clutter_actor_lower: Actor 'StBoxLayout' is not in the same container as actor 'StBoxLayout'
      JS LOG: Theme already patched: skip.
    JS ERROR: !!!   Exception in callback for signal: ready
    JS ERROR: !!!     message = '"appIconGrid.actor.get_first_child() is null"'
    JS ERROR: !!!     lineNumber = '64'
    JS ERROR: !!!     fileName = '"/home/michele/.local/share/gnome-shell/extensions/bolt@zacbarton.com/widgets/CategoryView.js"'
    JS ERROR: !!!     stack = '"([object Object],[object Array])@/home/michele/.local/share/gnome-shell/extensions/bolt@zacbarton.com/widgets/CategoryView.js:64
wrapper([object Object],[object Array])@/usr/share/gjs-1.0/lang.js:204
()@/home/michele/.local/share/gnome-shell/extensions/bolt@zacbarton.com/widgets/CategoryViewFiltered.js:47
wrapper()@/usr/share/gjs-1.0/lang.js:204
([object Object])@/home/michele/.local/share/gnome-shell/extensions/bolt@zacbarton.com/views/ContactsView.js:21
_emit("ready")@/usr/share/gjs-1.0/signals.js:124
()@/home/michele/.local/share/gnome-shell/extensions/bolt@zacbarton.com/data/Contacts.js:28

(gnome-shell:14118): St-ERROR **: st_widget_get_theme_node called on the widget [0x325b730 ShellStack.panels] which is not in the stage.

The "fatal error" is the last, but the others are probably related. Perhaps some ( actor.get_stage() !== null ) checks could at least prevent the Shell crash.