Fix: Handle empty AP (coscine/issues#1931)

src/SemanticSearch/RdfClient.cs

@@ -13,7 +13,7 @@ namespace Coscine.SemanticSearch
     /// <summary>
     /// Provides all necessary queries to the RDF database to create a mapping of metadata graphs into a document.
     /// </summary>
-    public class RdfClient 
+    public class RdfClient
     {
         public const string LABEL_LITERAL_RULE = "instance";
         public const string LABEL_ADDITIONAL_RULE = "graph";
@@ -62,6 +62,10 @@ namespace Coscine.SemanticSearch
             }} LIMIT 1";
             _queryString.SetUri("uri", new Uri(graphName));
             var results = _connector.QueryWithResultSet(_queryString);
+            if (results.Count == 0)
+            {
+                return null;
+            }
             return results.First().Value("applicationProfile").ToString();
         }
 
@@ -192,7 +196,7 @@ namespace Coscine.SemanticSearch
 
             // Expected correct URI format for Projects: https://purl.org/coscine/projects/{ProjectGUID}
             var projectRoleModel = new ProjectRoleModel();
-            return projectRoleModel.GetAllWhere(p => p.UserId.Equals(Guid.Parse(user)) && p.Project.Deleted == false).Select(p => $"https://purl.org/coscine/projects/{p.ProjectId}").ToList();           
+            return projectRoleModel.GetAllWhere(p => p.UserId.Equals(Guid.Parse(user)) && p.Project.Deleted == false).Select(p => $"https://purl.org/coscine/projects/{p.ProjectId}").ToList();
         }
 
         /// <summary>
@@ -329,7 +333,7 @@ namespace Coscine.SemanticSearch
             }} ORDER BY ?order";
             _queryString.SetUri("uri", new Uri(graphName));
             var results = _connector.QueryWithResultSet(_queryString);
-            
+
             return results.ToDictionary(
                 x => x.Value("class").ToString(),
                 x =>
@@ -466,13 +470,13 @@ namespace Coscine.SemanticSearch
                 foreach (var graph in documents.Keys)
                 {
                     jObjects.Add(graph, CreateFields(documents[graph], profile, indexMapper));
-                }                
-            } 
+                }
+            }
             else if (documents.Count() > 0)
             {
                 jObjects.Add(graphName, CreateFields(documents[graphName], profile, indexMapper));
             }
-            
+
             return jObjects;
         }
 
@@ -503,11 +507,17 @@ namespace Coscine.SemanticSearch
                 try
                 {
                     jObject.Merge(_dataTypeParser.Parse(label, triple.Object, indexMapper, profile));
-                } catch (NotIndexableException e)
+                }
+                catch (NotIndexableException e)
                 {
                     Console.WriteLine($"Property {property} could not be indexed. Reason: {e.Reason}");
                     continue;
                 }
+                catch (FormatException e)
+                {
+                    Console.WriteLine($"Property {property} could not be indexed. Reason: {e.Message}");
+                    continue;
+                }
             }
             return jObject;
         }