fixed: handler 可能为非HandlerMethod 类型的异常

xxl-job-admin/src/main/java/com/xxl/job/admin/controller/resolver/WebExceptionResolver.java

@@ -34,11 +34,13 @@ public class WebExceptionResolver implements HandlerExceptionResolver {
 
 		// if json
 		boolean isJson = false;
+		if (handler instanceof HandlerMethod) {
 			HandlerMethod method = (HandlerMethod)handler;
 			ResponseBody responseBody = method.getMethodAnnotation(ResponseBody.class);
 			if (responseBody != null) {
 				isJson = true;
 			}
+		}
 
 		// error result
 		ReturnT<String> errorResult = new ReturnT<String>(ReturnT.FAIL_CODE, ex.toString().replaceAll("\n", "<br/>"));