Fixed a segfault in socket.c

0  0x00007f443f01a254 in _IO_vfprintf_internal (s=<optimized out>, format=<optimized out>, ap=<optimized out>) at vfprintf.c:1649
1  0x00007f443f01aebf in buffered_vfprintf (s=s@entry=0x7f443f376080 <_IO_2_1_stderr_>, format=format@entry=0x422498 "Got error while receiving a message from clsyncsock with sock %u: %s (errno: %u)",
    args=args@entry=0x7f443dd8cd80) at vfprintf.c:2318
2  0x00007f443f015cbe in _IO_vfprintf_internal (s=0x7f443f376080 <_IO_2_1_stderr_>, format=0x422498 "Got error while receiving a message from clsyncsock with sock %u: %s (errno: %u)", ap=0x7f443dd8cd80)
    at vfprintf.c:1301
3  0x0000000000404ffe in vprintf_stderr (fmt=0x422498 "Got error while receiving a message from clsyncsock with sock %u: %s (errno: %u)", args=0x7f443dd8cd80) at error.c:69
4  0x0000000000405795 in _error (function_name=0x422720 <__FUNCTION__.5185> "socket_procclsyncsock", fmt=0x422498 "Got error while receiving a message from clsyncsock with sock %u: %s (errno: %u)")
    at error.c:232
5  0x00000000004199ec in socket_procclsyncsock (arg=0x63b020 <sockthreaddata>) at socket.c:617
6  0x00007f443f382e0e in start_thread (arg=0x7f443dd8e700) at pthread_create.c:311
7  0x00007f443f0b793d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113