fix(接口测试): 删除没有用例的接口定义会报错

--bug=1014506 --user=陈建星 【测试跟踪】功能用例关联测试，接口/场景/性能用例删除后，关联的测试用例没有同步删除 https://www.tapd.cn/55049933/s/1193457

backend/src/main/java/io/metersphere/track/service/TestPlanApiCaseService.java

@@ -139,6 +139,9 @@ public class TestPlanApiCaseService {
     }
 
     public int deleteByCaseIds(List<String> caseIds) {
+        if (CollectionUtils.isEmpty(caseIds)) {
+            return 0;
+        }
         TestPlanApiCaseExample example = new TestPlanApiCaseExample();
         example.createCriteria()
                 .andApiCaseIdIn(caseIds);