Update: fixes

src/SQL2Linked/Implementations/ResourceStructuralData.cs

@@ -65,12 +65,15 @@ namespace SQL2Linked.Implementations
                     }
                 }
 
+                if (entry.Keywords.Any())
+                {
                     var listKeywords = entry.Keywords.Split(';').ToList();
                     foreach (var keyword in listKeywords)
                     {
                         AssertToGraphLiteralNode(graph, resourceGraphName, dcterms + "subject", keyword);
                         Console.WriteLine($"For resource '{entry.DisplayName}' will migrate triple '{resourceGraphName} {dcterms}subject {keyword}'. ");
                     }
+                }
 
                 AssertToGraphLiteralNode(graph, resourceGraphName, dcterms + "rights", entry.UsageRights);
                 Console.WriteLine($"For resource '{entry.DisplayName}' will migrate triple '{resourceGraphName} {dcterms}rights {entry.UsageRights}'. ");