This would try reading from an uninitialized buffer thereby resulting
in a bad audio glitch. This does two things to fix the problem:
1) When there are no input nodes attached to an input bus, nothing is
read and 0 will be returned for the frames read variable.
2) The buffer is silenced by default.
This fixes a bug with ma_engine where it would glitch in the moment
just after the engine is initialized and before a sound or group is
attached.
This is needed for scheduling frame-exact starting and stopping of
nodes, in addition to any kind of time-based effects required by custom
nodes, such as fading.
With this change, attachment and detachment of a node's output bus is
now consistent:
* ma_node_attach_output_bus()
* ma_node_detach_output_bus()
The old function that allowed you to attach the other way around has
been removed as the caller can easily do that themselves by swapping
the order of parameters.
David Reid