rem: void buffersize_changed(void) { child->buffersize(buffersize(), samples_per_second()); }
add: void buffersize_changed(void) { if (child != 0) child->buffersize(buffersize(), samples_per_second()); }
context:   void buffersize_changed(void) { child->buffersize(buffersize(), samples_per_second()); }