fixed bug related to multiple drag and drop initializations

dist/kinetic-core.js

@@ -628,7 +628,7 @@ Kinetic.Node.prototype = {
      */
     draggable: function(isDraggable) {
         if(this.draggable !== isDraggable) {
-            if(isDraggable) {
+            if(isDraggable && this.isDragging()) {
                 this._initDrag();
             }
             else {
@@ -1187,7 +1187,15 @@ Kinetic.Stage.prototype = {
                     addLayer(n);
                 }
                 else {
-                    callback(bufferLayer.getCanvas().toDataURL(mimeType, quality));
+                    try {
+                        // If this call fails (due to browser bug, like in Firefox 3.6),
+                        // then revert to previous no-parameter image/png behavior
+                        callback(bufferLayer.getCanvas().toDataURL(mimeType, quality));
+                    }
+                    catch(exception)
+                    {
+                        callback(bufferLayer.getCanvas().toDataURL());
+                    }
                 }
             };
             imageObj.src = dataURL;