QAudioOutput fails to handle QAudioFormat with more than 6 channels

I tried audiooutput from qtmultimedia5 examples.

I just made one modification.
In audiooutput.cpp file, I replaced following line:
m_format.setChannelCount(1);
by:
m_format.setChannelCount(7);

After successful compilation, program received SIGABRT and write following lines:
Assertion 's' failed at pulse/stream.c:2110, function pa_stream_set_state_callback(). Aborting.

Program works as expected with channel count values from 1 to 6.
Program fails with channel count values from 7 to 16.

By looking here, https://github.com/pulseaudio/pulseaudio/blob/master/src/pulse/stream.c, it seems Qt code called pa_stream_set_state_callback function provided by pulseaudio with a null pointer.