### Current Behavior Use api-breaker to set circuit breaker ### Expected Behavior When the upstream service is not available, return my desired json ### Error Logs   ### Steps to Reproduce 1.configure api-breaker of plugin `{ "break_response_code": 200, "max_breaker_sec": 300, "unhealthy": { "http_statuses": [ 500, 502, 503 ], "failures": 3 }, "healthy": { "http_statuses": [ 200 ], "successes": 3 }, "break_response_body": "{\"code\":\"0\",\"msg\":\"new json body\"}", "break_response_headers": [{"content-type":"application/json"}] }` 2.When I remove break_response_headers, the plugin works fine ### Environment - Kubernetes version: v1.18.15 - APISIX version : apache/apisix:2.14.1-alpine - Ingress Controller: apache/apisix-ingress-controller:1.4.1 - etcd version: docker.io/bitnami/etcd:3.4.14-debian-10-r0 - APISIX Dashboard version: 2.11.0