Frequent coredumps during MP3 playback

```
What steps will reproduce the problem?

Playing back FLAC files doesn't cause any issue. MP3 files, however, do.
After awhile, it will segfault.

What version of the product are you using? On what operating system?

Squeezelite 1.6.4 on Debian jessie x86_64

Please provide any additional information below.

I also filed this in the Debian BTS at
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=774524

Core was generated by `squeezelite -a 200 10 -d output debug -o dmix -u
hLX'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007f09756a6bbc in resample_drain (process=0x7f09758b3600
) at resample.c:108
108 clip_cnt = *(SOXR(r, num_clips, r->resampler));
(gdb) bt
#0 0x00007f09756a6bbc in resample_drain (process=0x7f09758b3600
) at resample.c:108
#1 0x00007f09756a6411 in process_drain () at process.c:109
#2 0x00007f097569abd0 in decode_thread () at decode.c:87
#3 0x00007f09752530a4 in start_thread (arg=0x7f0975615700) at
pthread_create.c:309
#4 0x00007f097258bccd in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:111
(gdb)

(gdb) print r
$1 = (struct soxr *) 0x7f09767729c0
(gdb) print r->resampler
$2 = (soxr_t) 0x0

```

Original issue reported on code.google.com by `rm.rf.do...@gmail.com` on 5 Jan 2015 at 2:57