fix(接口测试): 修复删除引用的场景后，无法再次添加步骤的缺陷

--bug=1030999 --user=王孝刚 【接口测试】编辑场景-引用场景-展开选中子步骤-删除引用的场景-点击导入场景失败 https://www.tapd.cn/55049933/s/1434447

api-test/frontend/src/business/automation/scenario/EditApiScenario.vue

@@ -1512,10 +1512,12 @@ export default {
       this.showAll();
       this.buttonData = buttons(this);
       this.initPlugins();
+      this.selectedTreeNode = undefined;
+      this.selectedNode = undefined;
     },
     fabClick() {
       if (this.operatingElements && this.operatingElements.length < 1) {
-        if ((this.selectedTreeNode && this.selectedTreeNode.referenced === 'REF') || this.selectedTreeNode.disabled) {
+        if ((this.selectedTreeNode && this.selectedTreeNode.referenced === 'REF') || (this.selectedTreeNode.disabled && this.selectedTreeNode.disabled)) {
           this.$warning(this.$t('api_test.scenario.scenario_warning'));
         } else {
           this.$warning(this.$t('api_test.scenario.scenario_step_warning'));

api-test/frontend/src/business/automation/scenario/maximize/MaximizeScenario.vue

@@ -600,6 +600,7 @@ export default {
     outsideClick(e) {
       e.stopPropagation();
       this.showAll();
+      this.selectedNode = undefined;
     },
     fabClick() {
       if (this.operatingElements.length < 1) {