fixed: checked port

Author: salgum1114

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "react-design-editor",
-	"version": "0.0.85",
+	"version": "0.0.86",
 	"description": "Design Editor Tools with React.js + ant.design + fabric.js",
 	"main": "dist/react-design-editor.cjs.js",
 	"module": "dist/react-design-editor.es.js",

src/canvas/handlers/LinkHandler.ts

@@ -142,8 +142,8 @@ class LinkHandler {
 		}
 		this.handler.canvas.renderAll();
 		link.setPort(fromNode, fromPort, toNode, toPort);
-		fromPort.setConnected?.(true);
-		toPort.setConnected?.(true);
+		fromPort?.setConnected?.(true);
+		toPort?.setConnected?.(true);
 		this.handler.portHandler.setCoords(fromNode);
 		this.handler.portHandler.setCoords(toNode);
 		this.handler.canvas.requestRenderAll();