last slice encoded with qoaenc is not padded to size 8

[richardpl]

This causes segmentation fault if build with -fsanitize=address

So many qoaenc encoded files are invalid in last frame.

Workaround is to just set missing bytes to 0 as they are not actually used in decoding, but this complicates code path and ultimately breaks optimizations, and makes sanity checks within decoder less straightforward.

[richardpl]

Actually files are ok, was bug in code...