Call show() on new dialogs

- run() was removed from the dialog because it blocks

gajim/gtk/themes.py

@@ -325,7 +325,7 @@ class Themes(Gtk.ApplicationWindow):
             _('Do you want to permanently delete this theme?'),
             [DialogButton.make('Cancel'),
              DialogButton.make('Delete', callback=_remove_theme)],
-            transient_for=self)
+            transient_for=self).show()
 
     @staticmethod
     def _on_destroy(*args):

gajim/history_manager.py

@@ -577,7 +577,7 @@ class HistoryManager:
                      paths_len, liststore[list_of_paths[0]][0]),
             [DialogButton.make('Cancel'),
              DialogButton.make('Delete', callback=on_ok)],
-            transient_for=self._ui.history_manager_window)
+            transient_for=self._ui.history_manager_window).show()
 
     def _delete_logs(self, liststore, list_of_paths):
         paths_len = len(list_of_paths)
@@ -614,7 +614,7 @@ class HistoryManager:
                      paths_len),
             [DialogButton.make('Cancel'),
              DialogButton.make('Delete', callback=on_ok)],
-            transient_for=self._ui.history_manager_window)
+            transient_for=self._ui.history_manager_window).show()
 
     def on_search_db_button_clicked(self, widget):
         text = self._ui.search_entry.get_text()