Function ensureError

Ensures that an error is an actual instance of an error.

• If it's null or undefined - it is wrapped as UnexpectedNullUndefined MosaicError. In this case, there might be a bug somewhere that throws null or undefined.
• If it's an instance of an error - passed error is returned as is.
• If it's not an instance of an error - it is wrapped as Unhandled MosaicError. In this case, custom handling of error might be required.

Unlike type assertion, you must use the newly returned value.