can't change password

[ginuerzh]

I use ejabberd 16.03 on ubuntu 14.04

my mod_restful config:

listen:

port: 5289
module: ejabberd_http
request_handlers:
    "/api": mod_restful

mod_restful:
api:
-
path: ["admin"]
module: mod_restful_admin
params:
key: "admin"
allowed_commands: [register, unregister]
-
path: ["register"]
module: mod_restful_register
params:
key: "admin"

First I register an account, that's ok.
but when I want to change the password:

http://localhost:5289/api/register/change_password

the log tell me:
[error] <0.18174.0> Processing throwed error undef
trace: [{ejabberd_auth,check_password,[<<"abcdefg">>,<<"localhost">>,<<"123456">>],[]},{mod_restful_register,post_change_password,1,[{file,"src/mod_restful_register.erl"},{line,124}]},{mod_restful,handle_rest_request,5,[{file,"src/mod_restful.erl"},{line,193}]},{mod_restful,process,2,[{file,"src/mod_restful.erl"},{line,161}]},{ejabberd_http,process,5,[{file,"src/ejabberd_http.erl"},{line,363}]},{ejabberd_http,process_request,1,[{file,"src/ejabberd_http.erl"},{line,451}]},{ejabberd_http,process_header,2,[{file,"src/ejabberd_http.erl"},{line,291}]},{ejabberd_http,parse_headers,1,[{file,"src/ejabberd_http.erl"},{line,211}]}]