session CHANGE refuse sessions without locks
diff --git a/src/session.c b/src/session.c
index 9a8153e..9ed564a 100644
--- a/src/session.c
+++ b/src/session.c
@@ -281,6 +281,9 @@
         } else {
             locked = 1;
         }
+    } else {
+        ERRINT;
+        return;
     }
 
     if ((session->side == NC_CLIENT) && (session->status == NC_STATUS_RUNNING) && locked) {