fix: app data为空设为null

server/src/main/java/com/pica/cloud/online/exam/analysis/server/controller/AnalysisController.java

@@ -400,7 +400,7 @@ public class AnalysisController {
     }
 
     @ApiOperation(value = "回复", response = PicaResponse.class)
-    @RequestMapping(value = "/reply/{examTitleId}", method = RequestMethod.POST, produces = "application/x-www-form-urlencoded;charset=UTF-8")
+    @RequestMapping(value = "/reply/{examTitleId}", method = RequestMethod.POST, produces = "application/json;charset=UTF-8")
     public PicaResponse reply( @PathVariable("examTitleId") Integer examTitleId,
                                @RequestParam String content,
                                @RequestHeader String token) {