I tried mounting a horse bareback in SMP and the server kicks me: Internal Exception - NullPointerException.

There's no stacktrace on the server console, only me disconnecting and a single line of debug code.

2013-04-18 18:24:12 [INFO] SnoFox[/67.182.0.0:49634] logged in with entity id 1041 at (1026.2139547745503, 68.7000000178814, 600.816943866349)
[GC 339666K->164539K(1034048K), 0.1117042 secs]
2013-04-18 18:24:13 [SEVERE] Reached end of stream
2013-04-18 18:24:13 [INFO] SnoFox lost connection: disconnect.endOfStream
removing player mount