diff -r f3da1f26f949 -r d5219b039120 client/js/paper-renderer.js
--- a/client/js/paper-renderer.js	Tue May 14 12:36:11 2013 +0200
+++ b/client/js/paper-renderer.js	Tue May 14 12:54:42 2013 +0200
@@ -627,16 +627,14 @@
 };
 
 Rkns.Renderer.Edge.prototype.redraw = function() {
-    this.from_representation = this.renderer.getRepresentationByModel(this.model.get("from"));
-    this.to_representation = this.renderer.getRepresentationByModel(this.model.get("to"));
-    if (!this.from_representation || !this.to_representation) {
-/*
-    console.log(
-            "Error on edge " + this.model.get("id")
-            + " from " + (this.model.get("from") ? this.model.get("from").get("id") : "<null>")
-            + " to " + (this.model.get("to") ? this.model.get("to").get("id") : "<null>")
-    );
-*/
+    var from = this.model.get("from"),
+        to = this.model.get("to");
+    if (!from || !to) {
+        return;
+    }
+    this.from_representation = this.renderer.getRepresentationByModel(from);
+    this.to_representation = this.renderer.getRepresentationByModel(to);
+    if (typeof this.from_representation === "undefined" || typeof this.to_representation === "undefined") {
         return;
     }
     var _p0a = this.from_representation.paper_coords,
@@ -2208,6 +2206,9 @@
 };
 
 Rkns.Renderer.Scene.prototype.getRepresentationByModel = function(_model) {
+    if (!_model) {
+        return undefined;
+    }
     return Rkns._(this.representations).find(function(_repr) {
         return _repr.model === _model;
     });