Reproduction steps:
1. Create a new project
2. Setup Google Sheet Service
3. Create a Table
4. Add an empty Key and push it to a Spreadsheet

Expected result: NullReferenceException is not outputted when pushing empty string to Google Sheets
Actual result: NullReferenceException when pushing empty string to Google Sheets

Reproducible on: Localization 1.0.0-pre.9 (2019.4.27f1, 2020.3.10f1, 2021.1.9f1, 2021.2.0a17)
Not reproducible on: Localization 0.7.1-preview - 1.0.0-pre.8 (2019.4.27f1, 2020.3.10f1, 2021.1.9f1, 2021.2.0a17)

Notes:
-Exception:
Push `New Table` to Google Sheets: Failed
Object reference not set to an instance of an object
UnityEngine.UnitySynchronizationContext:ExecuteTasks ()
-Issue can be fixed locally by modifying GoogleSheets.cs line 389:
if (tableEntries.Length > 0 && (tableEntries\[0]?.SharedEntry?.Metadata?.HasMetadata<ExcludeEntryFromExport>() ?? false)) continue;