Don't load settings if the greeter settings directory is empty (refs: #17136)

This allows us to avoid showing the "Settings were loaded" notification
on the first boot after configuring the persistent volume.

This will not be required anymore once #11529 is done, i.e. settings are
persisted immediately after configuring the persistent volume.

config/chroot_local-includes/usr/lib/python3/dist-packages/tailsgreeter/ui/main_window.py

@@ -133,7 +133,7 @@ class GreeterMainWindow(Gtk.Window, TranslatableWindow):
         self.listbox_settings.set_placeholder(self.label_settings_default)
 
         # Persistent storage
-        self.persistent_storage = PersistentStorage(self.persistence_setting, self.load_settings, builder)
+        self.persistent_storage = PersistentStorage(self.persistence_setting, self.load_settings, self.apply_settings, builder)
 
         # Add children to ApplicationWindow
         self.add(self.box_main)
@@ -178,6 +178,10 @@ class GreeterMainWindow(Gtk.Window, TranslatableWindow):
 
     # Actions
 
+    def apply_settings(self):
+        for setting in self.settings:
+            setting.apply()
+
     def load_settings(self):
         # We have to load formats and keyboard before language, because
         # changing the language also changes the other two, which causes

config/chroot_local-includes/usr/lib/python3/dist-packages/tailsgreeter/ui/persistent_storage.py

 import logging
 import gi
+import os
 import threading
 from typing import TYPE_CHECKING, Callable
 
 from tailsgreeter.ui import _
+from tailsgreeter.config import settings_dir
 
 gi.require_version('GLib', '2.0')
 gi.require_version('Gtk', '3.0')
@@ -14,9 +16,10 @@ if TYPE_CHECKING:
 
 
 class PersistentStorage(object):
-    def __init__(self, persistence_setting: "PersistenceSettings", load_settings_cb: Callable, builder):
+    def __init__(self, persistence_setting: "PersistenceSettings", load_settings_cb, apply_settings_cb: Callable, builder):
         self.persistence_setting = persistence_setting
         self.load_settings_cb = load_settings_cb
+        self.apply_settings_cb = apply_settings_cb
 
         self.box_storage = builder.get_object('box_storage')
         self.box_storage_unlock = builder.get_object('box_storage_unlock')
@@ -110,7 +113,10 @@ class PersistentStorage(object):
         self.box_storage_unlocked.set_visible(True)
         self.button_start.set_sensitive(True)
 
-        self.load_settings_cb()
+        if not os.listdir(settings_dir):
+            self.apply_settings_cb()
+        else:
+            self.load_settings_cb()
 
     def cb_checkbutton_storage_show_passphrase_toggled(self, widget):
         self.entry_storage_passphrase.set_visibility(widget.get_active())