Crash when attempting to auto open the same database between two unlocking databases

[droidmonkey]

Overview

Steps to Reproduce

1. Open two databases that point to the same auto open database
2. Unlock DB 1
3. Quickly unlock DB 2
4. 🤯

Expected Behavior

No crash

Actual Behavior

Random location crashes when DB 2 unlock wipes out the auto open database pointer held by DatabaseWidget which is currently unlocking the database.

Context

To fix this we need to add an unlock guard to DatabaseWidget to prevent successive unlock attempts from occurring.