Here's the Trace logs:
DataMashup.Trace Information: 24579 : {"Start":"2016-11-16T16:07:39.3423215Z","Action":"Engine/IO/OData/Create","ServiceUri":"https://microsoft.sharepoint.com/teams/Revolution_edu_team/_vti_bin/ListData.svc","RequestUrl":"https://microsoft.sharepoint.com/teams/Revolution_edu_team/_vti_bin/ListData.svc","RequestHeaders":"null","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:00.4101442"}
DataMashup.Trace Information: 24579 : {"Start":"2016-11-16T16:07:39.3310555Z","Action":"SimpleDocumentEvaluator/GetResult/Evaluate","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:00.4218350"}
DataMashup.Trace Information: 24579 : {"Start":"2016-11-16T16:07:39.7529449Z","Action":"BackgroundThread/RollingTraceWriter/Flush","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"00000000-0000-0000-0000-000000000000","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":12,"Duration":"00:00:00.0016985"}
DataMashup.Trace Information: 24579 : {"Start":"2016-11-16T16:07:41.3091112Z","Action":"Engine/IO/OData/Request","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:00.0001039"}
DataMashup.Trace Error: 24579 : {"Start":"2016-11-16T16:07:42.3301344Z","Action":"Engine/IO/OData/GetResponse","RequestUri":"https://microsoft.sharepoint.com/teams/Revolution_edu_team/_vti_bin/ListData.svc/TeamTracking?$top=1000","RequestMethod":"GET","Exception":"Exception:\r\nExceptionType: System.Net.WebException, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\r\nMessage: The remote server returned an error: (500) Internal Server Error.\r\nStackTrace:\n at System.Net.HttpWebRequest.GetResponse()\r\n at Microsoft.Mashup.Engine1.Library.OData.ODataRequest.GetResponse(WebRequest webRequest)\r\n\r\n\r\n","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:00.9034242"}
DataMashup.Trace Warning: 24579 : {"Start":"2016-11-16T16:07:41.2890643Z","Action":"Library/Common/RetryPolicy/TryExecuteAction","Attempt":"1","Exception":"Exception:\r\nExceptionType: System.Net.WebException, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\r\nMessage: The remote server returned an error: (500) Internal Server Error.\r\nStackTrace:\n at System.Net.HttpWebRequest.GetResponse()\r\n at Microsoft.Mashup.Engine1.Library.OData.ODataRequest.GetResponse(WebRequest webRequest)\r\n at Microsoft.Mashup.Engine1.Library.Web.Request.ManualRedirect(IEngineHost host, String resourceKind, Uri uri, CreateWebRequestDelegate createRequest, Func`2 createResponse, WebRequest& webRequest, Int32[] nonErrors)\r\n at Microsoft.Mashup.Engine1.Library.OData.ODataRequest.<>c__DisplayClass1.<GetResponseStream>b__0()\r\n at Microsoft.Mashup.Engine1.Library.Common.RetryPolicy.Execute[TResult](IEngineHost host, Func`1 func)\r\n\r\n\r\n","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:01.9482311"}
DataMashup.Trace Error: 24579 : {"Start":"2016-11-16T16:07:41.2884307Z","Action":"Library/Common/RetryPolicy/ExecuteAction","TryCount":"3","RetryAlgorithm":"ExponentialBackoff","Exception":"Exception:\r\nExceptionType: System.Net.WebException, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\r\nMessage: The remote server returned an error: (500) Internal Server Error.\r\nStackTrace:\n at System.Net.HttpWebRequest.GetResponse()\r\n at Microsoft.Mashup.Engine1.Library.OData.ODataRequest.GetResponse(WebRequest webRequest)\r\n at Microsoft.Mashup.Engine1.Library.Web.Request.ManualRedirect(IEngineHost host, String resourceKind, Uri uri, CreateWebRequestDelegate createRequest, Func`2 createResponse, WebRequest& webRequest, Int32[] nonErrors)\r\n at Microsoft.Mashup.Engine1.Library.OData.ODataRequest.<>c__DisplayClass1.<GetResponseStream>b__0()\r\n at Microsoft.Mashup.Engine1.Library.Common.RetryPolicy.Execute[TResult](IEngineHost host, Func`1 func)\r\n\r\n\r\n","ProductVersion":"2.40.4554.463 (PBIDesktop)","ActivityId":"6c237b2a-0034-495d-b503-53ee9551bb45","Process":"Microsoft.Mashup.Container.NetFX40","Pid":13124,"Tid":1,"Duration":"00:00:01.9491566"}
That's the error I get with version 15, but how do I create a non-null but empty Collection value?