avoid a null ref

src/isnd/Data/Catalog/RegistrationPage.cs

@@ -71,7 +71,7 @@ namespace isnd.Data.Catalog
             }
             Upper = upper.ToFullString();
             Lower = lower.ToFullString();
-            if (latest != null)
+            if (latest != null && latest.LatestCommit !=null)
             {
                 CommitId = latest.CommitId;
                 CommitTimeStamp = latest.LatestCommit.CommitTimeStamp;