fix(接口测试): 修复部分接口导出swagger文件报错问题

--bug=1022261 --user=郭雨琦
https://www.tapd.cn/55049933/bugtrace/bugs/view/1155049933001022261

api-test/backend/src/main/java/io/metersphere/api/parse/api/Swagger3Parser.java

@@ -998,6 +998,7 @@ public class Swagger3Parser extends SwaggerAbstractParser {
 
         // 返回code
         JSONArray statusCode = response.optJSONArray("statusCode");
+        if (statusCode != null) {
             for (int i = 0; i < statusCode.length(); i++) {
                 JSONObject statusCodeInfo = new JSONObject();
                 statusCodeInfo.put("headers", headers);
@@ -1011,6 +1012,7 @@ public class Swagger3Parser extends SwaggerAbstractParser {
                     responseBody.put(jsonObject.optString("name"), statusCodeInfo);
                 }
             }
+        }
         return responseBody;
     }