[simple-scan] Don't use URI for changing extension.

[Bartosz <bkosiorek src gnome org>]

commit 365f3903ec85f57f42be25c7f58295e70e3ca00f
Author: Bartosz Kosiorek <gang65 poczta onet pl>
Date:   Tue Apr 14 23:24:19 2020 +0200

    Don't use URI for changing extension.
    
    Fixes: #165

 src/app-window.vala | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/src/app-window.vala b/src/app-window.vala
index 7ff08ae..3a16a68 100644
--- a/src/app-window.vala
+++ b/src/app-window.vala
@@ -572,8 +572,7 @@ public class AppWindow : Gtk.ApplicationWindow
                 settings.set_string ("save-format", mime_type);
             }
 
-            var uri = save_dialog.get_uri ();
-            var filename = Path.get_basename (uri);
+            var filename = save_dialog.get_current_name ();
 
             /* Replace extension */
             var extension_index = filename.last_index_of_char ('.');