segfault in qdrouterd when calling pn_link_name

#0  pn_string_get (string=0x0) at /usr/src/debug/qpid-proton-0.9/proton-c/src/object/string.c:120
#1  0x00007f1e9d31cfdc in pn_link_name (link=<optimized out>) at /usr/src/debug/qpid-proton-0.9/proton-c/src/engine/engine.c:1316
#2  0x00007f1e9d568ea4 in qd_router_link_name (link=0x7f1e8804dd20) at /usr/src/debug/qpid-dispatch-0.4/src/router_agent.c:90
#3  qd_entity_refresh_router_link (entity=0x118afd0, impl=0x7f1e8804dd20) at /usr/src/debug/qpid-dispatch-0.4/src/router_agent.c:98
#4  0x00007f1e90e53dac in ffi_call_unix64 () from /lib64/libffi.so.6
#5  0x00007f1e90e536d5 in ffi_call () from /lib64/libffi.so.6
#6  0x00007f1e91066c8b in _call_function_pointer (argcount=2, resmem=0x7fff0b6cfcd0, restype=<optimized out>, atypes=<optimized out>, 
    avalues=0x7fff0b6cfcb0, pProc=0x7f1e9d568e10 <qd_entity_refresh_router_link>, flags=4357)
    at /usr/src/debug/Python-2.7.5/Modules/_ctypes/callproc.c:832
#7  _ctypes_callproc (pProc=pProc@entry=0x7f1e9d568e10 <qd_entity_refresh_router_link>, 
    argtuple=argtuple@entry=({'linkType': 'endpoint', 'linkDir': 'out', 'type': u'org.apache.qpid.dispatch.router.link'}, 139769107766560), flags=4357, 
    argtypes=argtypes@entry=(<built-in method from_param of _ctypes.PyCSimpleType object at remote 0xfc6a50>, <built-in method from_param of _ctypes.PyCSimpleType object at remote 0xfdb420>), restype=<_ctypes.PyCSimpleType at remote 0xfd1120>, checker=0x0)
    at /usr/src/debug/Python-2.7.5/Modules/_ctypes/callproc.c:1179
#8  0x00007f1e91060a85 in PyCFuncPtr_call (self=<optimized out>, inargs=<optimized out>, kwds=<optimized out>)
    at /usr/src/debug/Python-2.7.5/Modules/_ctypes/_ctypes.c:3929
#9  0x00007f1e9c953073 in PyObject_Call (
    func=func@entry=<_FuncPtr(__name__='qd_entity_refresh_router_link') at remote 0x7f1e90ddc6d0>, 
    arg=arg@entry=({'linkType': 'endpoint', 'linkDir': 'out', 'type': u'org.apache.qpid.dispatch.router.link'}, 139769107766560), 
    kw=kw@entry=0x0) at /usr/src/debug/Python-2.7.5/Objects/abstract.c:2529
#10 0x00007f1e9c9e734c in do_call (nk=<optimized out>, na=2, pp_stack=0x7fff0b6d0000, 
    func=<_FuncPtr(__name__='qd_entity_refresh_router_link') at remote 0x7f1e90ddc6d0>)
    at /usr/src/debug/Python-2.7.5/Python/ceval.c:4316
#11 call_function (oparg=<optimized out>, pp_stack=0x7fff0b6d0000) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4121