Hi!

addTurboFilter() sets tailFilter incorrectly if newFilter.nextFilter != null

Here's what I was trying to do.
I implement a new TurboFilter.

This TurboFilter is an interceptor that captures log messages and stores them for analysis.
This is part of Unit Test. This Unit Test has to ensure that a specific message has been logged.

This TurboFilter is not configured via logback.xml
It can be but I don't want that to be mandatory.

Instead this TurboFilter needs to bind itself to LoggerContext programmatically, via Logback API.
It also need to bind itself as the first filter in the chain.

Here's how I've tried to do it:

final LogbackMessageProducer nuvo = new LogbackMessageProducer(true);

/* make sure we're the first in the chain */
final TurboFilter oldFirst = tfa.getFirstTurboFilter();
nuvo.setNext(oldFirst);

tfa.clearAllTurboFilters();
tfa.addTurboFilter(nuvo);

However should somebody else call addTurboFilter(some-other-filter) after this behavior shall be funny.
Basically all old turbo filters that were bound before my code executed shall be lost.