Fix invalid read when removing device
Fix invalid read when removing device

==13093== Invalid read of size 4
==13093==    at 0x40A632: ws_rmnode (ws.c:464)
==13093==    by 0x404450: msg_unregister (msg.c:141)
==13093==    by 0x40458D: node_hup_cb (msg.c:176)
==13093==    by 0x4E84049: g_main_context_dispatch (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4800.2)
==13093==    by 0x4E843EF: ??? (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4800.2)
==13093==    by 0x4E84711: g_main_loop_run (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4800.2)
==13093==    by 0x40379C: main (main.c:264)
==13093==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source