[tracker] tracker-preferences: Fix build with up-to-date gtk+ vapi

[Carlos Garnacho <carlosg src gnome org>]

commit 0a469ab0ac5d0470c84e952300bef25586953437
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Feb 28 20:51:52 2017 +0100

    tracker-preferences: Fix build with up-to-date gtk+ vapi
    
    The GtkListStore remove method now takes a ref TreeIter.

 src/tracker-preferences/tracker-preferences.vala |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/tracker-preferences/tracker-preferences.vala 
b/src/tracker-preferences/tracker-preferences.vala
index 10b92a0..79a7249 100644
--- a/src/tracker-preferences/tracker-preferences.vala
+++ b/src/tracker-preferences/tracker-preferences.vala
@@ -428,7 +428,7 @@ public class Tracker.Preferences {
                                Value value;
                                store.get_value (iter, 0, out value);
                                if (value.get_string () == to_check) {
-                                       store.remove (iter);
+                                       store.remove (ref iter);
                                        valid = store.get_iter_first (out iter);
                                } else {
                                        valid = store.iter_next (ref iter);
@@ -634,7 +634,7 @@ public class Tracker.Preferences {
                        // Check which UserDirectorys we match with str
                        UserDirectory[] matches = dir_match_user_directories (dir);
 
-                       store.remove (iter);
+                       store.remove (ref iter);
 
                        // Check if we need to untoggle a button
                        toggles_update (matches, false);