Can't set app-server to default values

Question

I'm trying to reset an app-server from an LDAP configuration to default values at the command line using REST but it appears to not be working. The external-security element does not exist on the JSON or the XML marklogic properties webpage located on the 8002 port if it is not set.

http://localhost:8002/manage/v2/servers/App-Services/properties?group\
-id=Default&format=json

I think this might be a bug. I've tried null, 0, \0, [], and many other forms of null in JSON. The XML form does not work either.

curl -X PUT --anyauth -u admin:$(cat pass) --header "Content-Type:application/json" \
-d '{"authentication":"digest", "internal-security":true,"default-user":"nobody",   \
"external-security":"" }'                                                           \
http://localhost:8002/manage/v2/servers/App-Services/properties?group-id=Default

Returns:

{"errorResponse":{"statusCode":"500", "status":"Internal Server Error", 
"messageCode":"XDMP-VALIDATEBADTYPE", "message":"XDMP-VALIDATEBADTYPE: (err:XQDY0027) 
validate strict { $nsfix } -- Invalid node type: srvprop:external-security lexical value 
\"\" invalid for expected type #srvprop:external-security at 
/srvprop:http-server-properties/srvprop:external-security using schema 
\"manage-server-properties.xsd\""}}