[banshee] Podcasting: Fix possible NRE

[AndrÃs Aragoneses <aaragoneses src gnome org>]

commit 2ceebee5d01343a96d26f0df22b59f387a7cd712
Author: AndrÃs G. Aragoneses <knocte gmail com>
Date:   Tue Sep 20 23:28:08 2011 +0100

    Podcasting: Fix possible NRE
    
    Fix possible NRE introduced in recent refactorings, oops.

 .../PodcastTrackListModel.cs                       |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)
---
diff --git a/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Data/PodcastTrackListModel.cs b/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Data/PodcastTrackListModel.cs
index 6af6890..d4acbcc 100644
--- a/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Data/PodcastTrackListModel.cs
+++ b/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Data/PodcastTrackListModel.cs
@@ -80,13 +80,15 @@ namespace Banshee.Podcasting.Gui
 
         protected override void GenerateSortQueryPart ()
         {
-            bool asc = SortColumn.SortType == Hyena.Data.SortType.Ascending;
-            SortQuery = (SortColumn == null)
-                ? GetSort ("PublishedDate", false)
-                : GetSort (SortColumn.SortKey, asc);
-
-            if (SortQuery == null) {
-                SortQuery =  Banshee.Query.BansheeQuery.GetSort (SortColumn.Field, asc);
+            bool asc = false;
+            if (SortColumn == null) {
+                SortQuery = GetSort ("PublishedDate", asc);
+            } else {
+                asc = SortColumn.SortType == Hyena.Data.SortType.Ascending;
+                SortQuery = GetSort (SortColumn.SortKey, asc);
+                if (SortQuery == null && SortColumn.Field != null) {
+                    SortQuery =  Banshee.Query.BansheeQuery.GetSort (SortColumn.Field, asc);
+                }
             }
         }