Working on restart resilience, hunting down multi-load mixer issue (still present)

apps/systemlib/mixer/mixer.cpp

@@ -54,6 +54,7 @@
 #include "mixer.h"
 
 Mixer::Mixer(ControlCallback control_cb, uintptr_t cb_handle) :
+	_next(nullptr),
 	_control_cb(control_cb),
 	_cb_handle(cb_handle)
 {

apps/systemlib/mixer/mixer_group.cpp

@@ -93,6 +93,7 @@ MixerGroup::reset()
 		mixer = _first;
 		_first = mixer->_next;
 		delete mixer;
+		mixer = nullptr;
 	}
 }