Fix segfault when adding a model via howdy-gtk

On all test machines available to me (3), the "map" event was apparently
fired before the "Please look directly into the camera" dialog was
finally created. Therefore, the dialog was not displayed at all when
scanning a face, and a segfault occurred when calling destroy().

Copied the code from onboarding.py, it works well there.

howdy-gtk/src/tab_models.py

@@ -3,6 +3,7 @@
 
 from i18n import _
 from gi.repository import Gtk as gtk
+from gi.repository import GObject as gobject
 
 
 def on_user_change(self, select):
@@ -71,13 +72,13 @@ def on_model_add(self, button):
 		dialog = gtk.MessageDialog(parent=self, flags=gtk.DialogFlags.MODAL, buttons=gtk.ButtonsType.NONE)
 		dialog.set_title(_("Creating Model"))
 		dialog.props.text = _("Please look directly into the camera")
-		dialog.get_child().connect("map", lambda w: execute_add(self, dialog, entered_name, self.active_user))
 		dialog.show_all()
 
+		# Wait a bit to allow the user to read the dialog
+		gobject.timeout_add(600, lambda: execute_add(self, dialog, entered_name))
 
-def execute_add(box, dialog, entered_name, user):
 
-	time.sleep(1)
+def execute_add(box, dialog, entered_name):
 
 	status, output = subprocess.getstatusoutput(["howdy add '" + entered_name + "' -y -U " + box.active_user])