avoided onHold event during addEdge

lib/network/mixins/ManipulationMixin.js

@@ -301,10 +301,12 @@ exports._createAddEdgeToolbar = function() {
   this.cachedFunctions["_manipulationReleaseOverload"] = this._manipulationReleaseOverload;
   this.cachedFunctions["_handleDragStart"] = this._handleDragStart;
   this.cachedFunctions["_handleDragEnd"] = this._handleDragEnd;
+  this.cachedFunctions["_handleOnHold"] = this._handleOnHold;
   this._handleTouch = this._handleConnect;
   this._manipulationReleaseOverload = function () {};
+  this._handleOnHold    = function () {};
   this._handleDragStart = function () {};
-  this._handleDragEnd = this._finishConnect;
+  this._handleDragEnd   = this._finishConnect;
 
   // redraw to show the unselect
   this._redraw();