[rygel] tracker: Don't add empty filter

[Jens Georg <jensgeorg src gnome org>]

commit d937a2ca1db59b884c159b5a02db7d5fb81e883d
Author: Jens Georg <mail jensge org>
Date:   Sun May 8 22:21:36 2016 +0200

    tracker: Don't add empty filter
    
    Signed-off-by: Jens Georg <mail jensge org>

 .../tracker/rygel-tracker-selection-query.vala     |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/src/plugins/tracker/rygel-tracker-selection-query.vala 
b/src/plugins/tracker/rygel-tracker-selection-query.vala
index b36bbe8..02123a0 100644
--- a/src/plugins/tracker/rygel-tracker-selection-query.vala
+++ b/src/plugins/tracker/rygel-tracker-selection-query.vala
@@ -174,7 +174,9 @@ public class Rygel.Tracker.SelectionQuery : Query {
         } catch (Error error) {};
 
         // Limit the files to a set of folders that may have been configured
-        filters.add (uri_filter);
+        if (uri_filter != null) {
+            filters.add (uri_filter);
+        }
 
         if (filters.size > 0) {
             query += " FILTER (";