优化登录返回错误结果为空js错误

@@ -268,8 +268,16 @@ layui.define(['sessions', 'form', 'common'],function (exports) {
                 },
                 error: function (xhr) {
                     layer.closeAll('loading');
-                    var error =JSON.parse(xhr.responseText) ;
-                    var error_msg = error.error_description ? error.error_description :error.resp_msg ;
+                    var error ;
+                    var error_msg;
+                    try {
+                        error =JSON.parse(xhr.responseText) ;
+                        error_msg = error.error_description ? error.error_description :error.resp_msg ;
+                    } catch (e){
+                        error = {
+                            status:500
+                        }
+                    }
                     if (xhr.status == 500){
                         error_msg = "服务器异常";
                     }else if (xhr.status == 0){