Reproduction steps:
1. Open project. (Attached by user)
2. Open new scene.
3. Open TestScript.cs.(Assets -> Scripts -> TestScript)
4. Replace code in line 6 with:
public LocalCardDBMS dbms = new LocalCardDBMS();
5. Uncomment 16 and 17 lines.
6. Create new empty GameObject.
7. Attach TestScript to that new GameObject.
8. Press Play.

Expected result: We will enter Play Mode and get some logs in console.
Actual result: Unity crashes.

Issue is caused by LocalCardDBMS.cs (Assets -> Scripts -> Database -> LocalCardDBMS):
~LocalCardDBMS()
{
Disconnect();
}

Reproduced on 5.3.0f4, 5.4.0f3, 5.4.3f1, 5.5.0f1, 5.6.0a3