FxMixer: ignore mute state in addChannelLeaf() to fix lockup

Even if we do not process the FX chain later, we at least have to enqueue
all related FX channels to the job queue in order to prevent a lockup.

src/core/FxMixer.cpp

@@ -443,7 +443,7 @@ void FxMixer::addChannelLeaf( int _ch, sampleFrame * _buf )
 	FxChannel * thisCh = m_fxChannels[_ch];
 
 	// if we're muted or this channel is seen already, discount it
-	if( thisCh->m_muteModel.value() || thisCh->m_queued )
+	if( thisCh->m_queued )
 	{
 		return;
 	}