fix: Fix showing status icon on flatpak

AppIndicator cannot access files within the flatpak container.

gajim/gtk/status_icon.py

@@ -303,7 +303,8 @@ class AppIndicatorIcon(GtkMenuBackend):
             'Gajim',
             'org.gajim.Gajim',
             AppIndicator.IndicatorCategory.COMMUNICATIONS)
-        self._status_icon.set_icon_theme_path(str(configpaths.get('ICONS')))
+        if not app.is_flatpak():
+            self._status_icon.set_icon_theme_path(str(configpaths.get('ICONS')))
         self._status_icon.set_status(AppIndicator.IndicatorStatus.ACTIVE)
         self._status_icon.set_menu(self._ui.systray_context_menu)
         self._status_icon.set_secondary_activate_target(