diff --git a/desktop/sources/scripts/listener.js b/desktop/sources/scripts/listener.js
index d68cc2f..6df0893 100644
--- a/desktop/sources/scripts/listener.js
+++ b/desktop/sources/scripts/listener.js
@@ -18,6 +18,7 @@ function Listener (dotgrid) {
   }
 
   function operate (data) {
+    if(!data){ return }
     if(!dotgrid.tool.layers[data.layer]){ return }
     dotgrid.tool.index = data.layer
     dotgrid.tool.addSegment(data.type, [data.from, data.to])