[BUG] JWT plugin throws ArrayIndexOutOfBoundsException for malformed Bearer header

### Current Behavior

The JWT plugin can throw `ArrayIndexOutOfBoundsException` when the incoming `Authorization` header contains the `Bearer` marker but does not contain a token in the expected second segment.

In current `origin/master`, `JwtPlugin.compatible()` does:

```java
return isAuth2(finalAuthorization) ? finalAuthorization.split(" ")[1] : finalAuthorization;
```

and `isAuth2()` only checks:

```java
return authorization.contains(AUTH2_TOKEN);
```

So values such as `Authorization: Bearer` or other malformed strings containing `Bearer` can pass `isAuth2()` and then fail at `split(" ")[1]`.

### Expected Behavior

Malformed JWT authorization headers should be rejected as an invalid token and return the normal unauthorized/error response instead of throwing an uncaught runtime exception.

### Steps to Reproduce

1. Enable the JWT plugin for a route.
2. Send a request with a malformed header, for example:

```http
Authorization: Bearer
```

3. The plugin attempts to access index `1` after splitting the header by a space.

### Code Location

- `shenyu-plugin/shenyu-plugin-security/shenyu-plugin-jwt/src/main/java/org/apache/shenyu/plugin/jwt/JwtPlugin.java`
- `compatible()`, lines around 100-113 in current `origin/master`

### Notes

If PR #6450 is intended to fix this path, this issue can be linked to that PR.