Access Violation when accessing REST service

I've built an interface to a thridparty Rest/Json web API, everything is working great with valid test cases, but when I request something invalid from the API, say a job that doesn't exist, the API returns a response where the body = 'null' and has a the content type as "application/json; charset=utf-8". I'm not sure if this is standard practice for a web API, but when I call Execute on the IHttpClient I end up with an Access Violation and the client exits.

Protrace is a follows

Exception code: C0000005 ACCESS_VIOLATION
Fault address: 00007FFC6733DAAD 01:000000000077CAAD C:\Apps\Progress\117\bin\prow.dll

** ABL Stack Trace **

--> Write OpenEdge.Net.HTTP.Filter.Payload.JsonEntityWriter at line 463 (OpenEdge/Net/HTTP/Filter/Payload/JsonEntityWriter.r)
ExtractEntity OpenEdge.Net.HTTP.Lib.ABLSockets.ABLSocketLibrary at line 360 (OpenEdge/Net/HTTP/Lib/ABLSockets/ABLSocketLibrary.r)
Execute OpenEdge.Net.HTTP.Lib.ABLSockets.ABLSocketLibrary at line 312 (OpenEdge/Net/HTTP/Lib/ABLSockets/ABLSocketLibrary.r)
Execute OpenEdge.Net.HTTP.HttpClient at line 154 (OpenEdge/Net/HTTP/HttpClient.r)
TryRest Tempo.TempoApi at line 1264 (D:\_Dev\OnTap-Trunk\rcode\Tempo\TempoApi.r)
ExecuteRest Tempo.TempoApi at line 234 (D:\_Dev\OnTap-Trunk\rcode\Tempo\TempoApi.r)


TryRest is:

METHOD PRIVATE INTEGER TryRest(
INPUT oUri AS URI,
INPUT cType AS CHARACTER,
INPUT cContentType AS CHARACTER,
INPUT oContent AS Object,
OUTPUT oResponse AS IHttpResponse ):

DEFINE VARIABLE result AS INTEGER NO-UNDO.

DEFINE VARIABLE oRequest AS IHttpRequest NO-UNDO.

CASE cType:

WHEN "GET" THEN
oRequest = RequestBuilder:GET(oURI)
:AddHeader("Authorization", "Bearer " + STRING(cAccessToken))
:AcceptJson()
:REQUEST.
END CASE.

oResponse = ResponseBuilder:Build():Response.
oClient:EXECUTE(oRequest,oResponse).

RETURN oResponse:StatusCode.

CATCH e AS Progress.Lang.Error:
UNDO, THROW e.
END CATCH.

END METHOD.


I'm using the latest OpenEdge client, 11.7.2 Windows x64.

My question is, is it normal for a web API to return 'Null' for an invalid request?

And secondly, this is obviously an unhandled exception in OpenEdge.Net.HTTP.Lib, which should not result in client crash.. Any ideas for working around it? I've tried changing AcceptJson() to AcceptAll, and AcceptHTML, but the protrace is the same, crashing in JsonEntityWriter.

Thanks

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