When the decoded audio size is exactly multiples of an internal
buffer size, the buffer's size becomes exactly zero when being
appended. In this case, createBuffer fails and the application
crashes.
This change fixes this issue by skipping to append a buffer in such
cases.
Closes#1635
If the source io.Reader's implementation is not good (e.g., Read
returns 0 if the buffer size is not multiples of 4), io.ReadFull
gets stuck forever. Instead, use reguler Read with a decent amount
of bytes buffer.
Closes#1599
