bug #I69UVL 如果switch返回为空或者null，无法选取到default组件

liteflow-testcase-el/liteflow-testcase-el-springboot/src/test/java/com/yomahub/liteflow/test/switchcase/SwitchELSpringbootTest.java

@@ -87,7 +87,7 @@ public class SwitchELSpringbootTest extends BaseTest {
     //switch返回如果是空，会走default选项
     @Test
     public void testSwitch8() throws Exception{
-        LiteflowResponse response = flowExecutor.execute2Resp("chain7", "arg");
+        LiteflowResponse response = flowExecutor.execute2Resp("chain8", "arg");
         Assert.assertTrue(response.isSuccess());
         Assert.assertEquals("a==>j==>d",response.getExecuteStepStr());
     }

liteflow-testcase-el/liteflow-testcase-el-springboot/src/test/resources/switchcase/flow.el.xml

@@ -46,8 +46,14 @@
     <chain name="chain7">
         THEN(
         a,
-        SWITCH(j).to(b, c).DEFAULT(d)
+        SWITCH(i).to(b, c).DEFAULT(d)
         );
     </chain>
 
+    <chain name="chain8">
+        THEN(
+        a,
+        SWITCH(j).to(b, c).DEFAULT(d)
+        );
+    </chain>
 </flow>