Fix: small fix for api

src/Tree/Controllers/TreeController.cs

@@ -338,7 +338,12 @@ namespace Coscine.Api.Tree.Controllers
             }
             else
             {
-                var tempGraph = new Graph();
+                var tempGraph = new Graph
+                {
+                    BaseUri = graphNameUri
+                };
+
+                tempGraph = new Graph();
                 StringParser.Parse(tempGraph, metadataObject.Value<string>("metadata"), MimeTypesHelper.GetParser(mimeType));
                 var triplesList = tempGraph.Triples.ToArray();
                 var subjectNode = tempGraph.CreateUriNode(graphNameUri);