Unhandled exception: Crash when updating package information.

* Description: Clicked the `Update Existing` button the `Metadata` menu.
* Version: 0.2.8
* OS: Windows-10-10.0.18362
* Type: `<class 'TypeError'>`
* Value: 'SimpleList' object is not iterable
* Traceback:
```
  File "creator\child_views\metadata_tab.py", line 65, in update_package
  File "creator\child_views\list_view.py", line 14, in __init__

```
