Unable to merge accounts

[jiannynan96]

{ "type": "https://stellar.org/horizon-errors/server_error", "title": "Internal Server Error", "status": 500, "detail": "An error occurred while processing this request. This is usually due to a bug within the server software. Trying this request again may succeed if the bug is transient, otherwise please report this issue to the issue tracker at: https://github.com/stellar/go/services/horizon/internal/issues. Please include this response in your issue.", "instance": "horizon-002c/BFEiaaFONB-48132104" }