I had a situation where I was doing:

    ma_backend backends[] = {
	ma_backend_jack,
	ma_backend_wasapi,
    };
    ma_context_init(backends, sizeof(backends)/sizeof(backends[0]),
	&contextConfig, &context);

And since JACK was unavailable, it fell back to WASAPI. When this
happened, the WASAPI commandIndex and commandCount variables were
already stomped on by the JACK backend initialization, but the WASAPI
backend assumes they are zero-initialized.
Signed-off-by: Steven Noonan <steven@uplinklabs.net>