Fails when attempting to list bookmarks before any exist

[SteveBenner]

Awesome script dude! You do however need to account for the case when no bookmarks exist, which is only on first run, currently.

REPRODUCE:

• Control-b before adding any bookmarks

Command 'BookmarksList' raised error.

Traceback (most recent call last):
  File "fman\impl\plugins\command_registry.py", line 128, in _execute_command
  File "C:\Users\sven\AppData\Roaming\fman\Plugins\Third-party\FmanBookmarks\bookmarks\__init__.py", line 31, in __call__
    result = show_quicksearch(self._listing)
  File "fman\__init__.py", line 235, in show_quicksearch
  File "fman\impl\util\qt\thread.py", line 11, in result
  File "fman\impl\util\qt\thread.py", line 81, in run_in_thread
  File "fman\impl\util\qt\thread.py", line 106, in result
  File "fman\impl\util\qt\thread.py", line 94, in __call__
  File "fman\impl\widgets.py", line 368, in show_quicksearch
  File "fman\impl\util\qt\thread.py", line 11, in result
  File "fman\impl\util\qt\thread.py", line 66, in run_in_thread
  File "fman\impl\widgets.py", line 383, in exec_dialog
  File "fman\impl\quicksearch.py", line 35, in exec
  File "fman\impl\quicksearch.py", line 108, in _update_items
  File "C:\Users\sven\AppData\Roaming\fman\Plugins\Third-party\FmanBookmarks\bookmarks\__init__.py", line 43, in _listing
    for item in self.bookmarks:
TypeError: 'NoneType' object is not iterable