[BUG] - FormatException when inserting documents with duplicate keys

[thanh-synaptive]

Version
4.1.2

Describe the bug
When inserting a document with a key which already exists, instead of throwing LiteException with with ErrorCode = INDEX_DUPLICATE_KEY, LiteDB throws FormatException.

Additional context

1. This is similar to System.FormatException: Input string was not in a correct format mbdavid/LiteDB#1115
2. It could lead to data corruption because the transaction may not be rolled back properly!
3. It seems the exception happens if a logger is used:

https://github.com/SynaptiveMedical/LiteDB/blob/synaptive/v4.1.2/LiteDB/Engine/LiteEngine.cs#L210
https://github.com/SynaptiveMedical/LiteDB/blob/synaptive/v4.1.2/LiteDB/Utils/Logger.cs#L69