Repro:
1. Open attached project.
2. Open Asset Table in Table Editor. (Assets/Localization/Tables/TestTable)
3. Click on Edit Table Entry Metadata button.
4. Set the table entry to 'None'.

Expected Result: Asset set to None, no errors.
Actual Result: Entry Metadata dropdown disappears, errors in console.

Reproducible in: 1.1.0, 1.0.0-pre.8.
Had some trouble testing earlier packages.

Tested in 2019.4.33f1.

Notes:
- Found when setting a texture asset to None.
- The issue does not occur if the metadata sidebar is not visible. (If you skip Step 3).
- Error messages in attached .txt