joinDialog: Fix detecting pointer devices
Gtk.get_current_event_device() is not available in GTK4.
This fixes the following error: TypeError: (intermediate value).get_current_event_device is not a function
Closes: #209
Edited by Balló György
Gtk.get_current_event_device() is not available in GTK4.
This fixes the following error: TypeError: (intermediate value).get_current_event_device is not a function
Closes: #209