update ControllerErrorHandler

web/src/main/java/cn/reghao/bnt/web/config/web/exception/ControllerErrorHandler.java

@@ -21,9 +21,13 @@ import jakarta.servlet.http.HttpServletRequest;
 public class ControllerErrorHandler implements ErrorController {
     @RequestMapping("/error")
     public String handleError(Model model, HttpServletRequest request) {
-        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
-        String prevUrl = (String) request.getAttribute("javax.servlet.forward.request_uri");
+        int statusCode = 500;
+        Object object = request.getAttribute("javax.servlet.error.status_code");
+        if (object != null) {
+            statusCode = (int) object;
+        }
 
+        String prevUrl = (String) request.getAttribute("javax.servlet.forward.request_uri");
         model.addAttribute("code", statusCode);
         if (statusCode == 404) {
             model.addAttribute("msg", "页面去火星啦～");