bug: plugin api-breaker set response headers occur 500 Internal Error

[he953481025-debug]

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