!10 修复 匿名用户会被鉴定为anonymousUser

Merge pull request !10 from niu_dehua/fix_login

src/main/java/cn/iocoder/dashboard/framework/security/core/util/SecurityFrameworkUtils.java

@@ -56,7 +56,7 @@ public class SecurityFrameworkUtils {
         if (authentication == null) {
             return null;
         }
-        return (LoginUser) authentication.getPrincipal();
+        return authentication.getPrincipal() instanceof LoginUser ? (LoginUser) authentication.getPrincipal() : null;
     }
 
     /**