Use actual buffer number instead of assuming sample buffers start at 0

[sixolet]

Previously, the lua code assumed that the sample buffers started with buffer number 0.

This was all cool when it was the only supercollider code running at the time, and all other buffers were clear when it started.

However, I wrote doubledecker to use a little buffer to optimize its white noise, and that was buffer 0, which caused mx. samples users to hear the noise and also kind of scrambled the keyboard.

[schollz]

Thanks! mx.samples shouldn't have worked before, lol!