[f-spot] Avoid occasional crasher during foldertree refresh.

[Ruben Vermeersch <rubenv src gnome org>]

commit 94a0ab8fbe1a3a5db8af283f342ce3ea1129de61
Author: Ruben Vermeersch <ruben savanne be>
Date:   Sat Jun 12 00:56:12 2010 +0200

    Avoid occasional crasher during foldertree refresh.

 src/Widgets/FolderTreeView.cs |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/Widgets/FolderTreeView.cs b/src/Widgets/FolderTreeView.cs
index 1addd7b..f69553e 100644
--- a/src/Widgets/FolderTreeView.cs
+++ b/src/Widgets/FolderTreeView.cs
@@ -70,7 +70,10 @@ namespace FSpot.Widgets
 			CellRendererPixbuf renderer = cell as CellRendererPixbuf;
 			
 			string stock;
-			File file = FileFactory.NewForUri (folder_tree_model.GetUriByIter (iter));
+			var uri = folder_tree_model.GetUriByIter (iter);
+			if (uri == null)
+				return;
+			File file = FileFactory.NewForUri (uri);
 			try {
 				FileInfo info =
 					file.QueryInfo ("standard::icon", FileQueryInfoFlags.None, null);