Update litegraph with upstream: middle mouse dragging.

web/lib/litegraph.core.js

@@ -6233,11 +6233,17 @@ LGraphNode.prototype.executeAction = function(action)
 																					,posAdd:[!mClikSlot_isOut?-30:30, -alphaPosY*130] //-alphaPosY*30]
 																					,posSizeFix:[!mClikSlot_isOut?-1:0, 0] //-alphaPosY*2*/
 																				});
-								
+							skip_action = true;
 						}
 					}
 				}
 			}
+
+			if (!skip_action && this.allow_dragcanvas) {
+            	//console.log("pointerevents: dragging_canvas start from middle button");
+            	this.dragging_canvas = true;
+            }
+
         	
         } else if (e.which == 3 || this.pointer_is_double) {