[shotwell] Use ngettext for export dialog title

[Jens Georg <jensgeorg src gnome org>]

commit 62c96ed53845943e629905ecc1e91fc00705dd44
Author: Jens Georg <mail jensge org>
Date:   Sun May 28 00:29:24 2017 +0200

    Use ngettext for export dialog title

 src/CollectionPage.vala |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/CollectionPage.vala b/src/CollectionPage.vala
index 15bab51..29bc96e 100644
--- a/src/CollectionPage.vala
+++ b/src/CollectionPage.vala
@@ -407,9 +407,9 @@ public abstract class CollectionPage : MediaPage {
 
         string title = null;
         if (has_some_videos)
-            title = (export_list.size == 1) ? _("Export Photo/Video") : _("Export Photos/Videos");
+            title = ngettext("Export Photo/Video", "Export Photos/Videos", export_list.size);
         else
-            title = (export_list.size == 1) ?  _("Export Photo") : _("Export Photos");
+            title = ngettext("Export Photo", "Export Photos", export_list.size());
         ExportDialog export_dialog = new ExportDialog(title);
 
         // Setting up the parameters object requires a bit of thinking about what the user wants.