heart: remove garbage appended to heart command

heart:get_cmd/0 is documented to return an empty string if the command is
cleared. get_cmd/0 returns 2 extra bytes: 1 byte for the trailing null,
1 byte from the op (the op is an unsigned char and 2 bytes are allocated
for it in the returned buffer).

1> heart:get_cmd().
{ok,[0,0]}
2> heart:set_cmd("echo hello").
ok
3> heart:get_cmd().
{ok,[101,99,104,111,32,104,101,108,108,111,0,0]}
4> heart:clear_cmd().
ok
5> heart:get_cmd().
{ok,[0,99]}

0 files changed, 0 insertions, 0 deletions