ListBox: Update docs of GtkListBoxUpdateHeaderFunc

before is always NULL for the first row.
listbox: Don't crash if cursor_row is NULL in real_focus

https://bugzilla.gnome.org/show_bug.cgi?id=708320
places sidebar: don't open a bookmark when clicking eject

Trying to open a bookmark which is being ejected is at best confusing.

https://bugzilla.gnome.org/show_bug.cgi?id=704087
Updated Traditional Chinese translation(Hong Kong and Taiwan)
Assamese translation updated
icontheme: Make sure icon_info->scale doesn't end up 0

GdkPixbuf will fail returning %NULL if we try to scale a pixbuf to (0, 0),
which will then trigger an assertion in gtk_icon_info_load_icon_finish();
we never want a scale of 0, so ensure it is at least 1.

https://bugzilla.gnome.org/show_bug.cgi?id=708384