Explorer card displays `loading...` when an empty directory is selected in fileOpenDialog

[nelsonni]

Describe the bug
Selecting any empty directory within the fileOpenDialog will result in an Explorer card instance that permanently holds the loading... state. This state was meant to provide a graceful default state while the directory content is loading, but in this case there will always be 0 sub-files and sub-directories.

To Reproduce
Steps to reproduce the behavior:

1. Launch Synectic
2. Go to File → Open...
3. Select any empty directory
4. Click the Open button
5. Wait for Explorer card to load
6. See error

Expected behavior
An icon and/or text indicating that the selected directory is empty.

Screenshots

Versions (please complete the following information):

• OS: MacOS, Windows, Linux
• Synectic Version: 1.0.0-beta (branch: development)

Additional context
Relevant code that checks and displaying the loading... state is available in Explorer.tsx:54-55.