fix bug.

src/components/wfd/components/Wfd.vue

@@ -206,6 +206,7 @@ export default {
           if (this.previous !== '') {
           if (this.previous !== '') {
             var previousValue = ''
             var previousValue = ''
             const item = this.graph.findById(this.previous[0])
             const item = this.graph.findById(this.previous[0])
+            if (item !== undefined) {
               previousValue = { ...item.getModel() }
               previousValue = { ...item.getModel() }
               var err = this.verifyProcess(previousValue)
               var err = this.verifyProcess(previousValue)
               if (err !== '') {
               if (err !== '') {
@@ -214,6 +215,7 @@ export default {
                 return
                 return
               }
               }
             }
             }
+          }
           const item = this.graph.findById(items[0])
           const item = this.graph.findById(items[0])
           this.selectedModel = { ...item.getModel() }
           this.selectedModel = { ...item.getModel() }
           this.previous = items
           this.previous = items