Add check that view exists for panel

There was a bug that the `quick_panel` prompt would not open when:

- There is at least 1 non-top level directory in the project
- The panel you are running the shortcut from, does not have any views open

The error that was coming up was:

```python
Traceback (most recent call last):
  File "./sublime_plugin.py", line 339, in run_
  File "./SublimeQuickFileCreator.py", line 108, in run
  File "./SublimeQuickFileCreator.py", line 20, in doCommand
  File "./SublimeQuickFileCreator.py", line 68, in move_current_directory_to_top
AttributeError: 'NoneType' object has no attribute 'file_name'
```

This pull request patches the bug as described above.