Token Based Rate limit policy failing when all optional parameters are not configured

[IsuruGunarathne]

Please select the area the issue is related to

Area/Policies (Policies, Policy Hub, Policy Engine etc)

Please select the aspect the issue is related to

Aspect/API (API backends, definitions, contracts, interfaces, OpenAPI)

Description

When the token based rate limit policy is configured with only one of the following optional parameters

The policy initialises successfully but fails at runtime when trying to delegate to advanced-ratelimit

Steps to Reproduce

1. Deploy a selfhosted ai-gateway with debug logs enabled for router, controller and polcy-engine
2. Deploy an OpenAI LLM provider
3. Add Token Based Ratelimit policy to the provider with only promptTokenLimits set
4. Save and redeploy the LLM provider
5. Notice the logs in the gateway, the policy chain would have successfully been updated
6. Make an api call to the provider
7. Notice the error logs in console

Severity Level of the Issue

Severity/Major (Important functionality is broken. Should be prioritized. Doesn't need immediate attention)

Environment Details (with versions)

No response