Telemetry with empty properties collection is dropped #319

            var properties = new Dictionary<string, string>
            {
                {"UserId", ""}
            };
            new TelemetryClient().TrackException(new ApplicationException(), properties);

Invalid json, no "," after properties collection.

Application Insights Telemetry: {"name":"Microsoft.ApplicationInsights.XXX.Exception","time":"2016-09-30T23:35:56.1080471Z","iKey":"XXX","tags":{"ai.internal.sdkVersion":"dotnet:2.2.0-31572","ai.operation.id":"/buMs/VxSMI=","ai.operation.name":"GET /Default","ai.operation.parentId":"/buMs/VxSMI=","ai.device.roleInstance":"ZZZ.redmond.corp.microsoft.com"},"data":{"baseType":"ExceptionData","baseData":{"ver":2,"handledAt":"UserCode","properties":{}"exceptions":[{"id":31494208,"typeName":"System.ApplicationException","message":"Error in the application.","hasFullStack":true}]}}}