[gnome-music] baseview: Fix the call to header_bar cancel button

[Marinus Schraal <mschraal src gnome org>]

commit 52e48618b9422ca3da71b0c188f849d6f8befa34
Author: Jean Felder <jean felder gmail com>
Date:   Mon Feb 5 15:50:43 2018 +0100

    baseview: Fix the call to header_bar cancel button
    
    PlaylistView view does not have a set_selection_mode method. This
    causes a crash when the cancel_selection button is called from any
    view. Use unselect_all from BaseView to prevent it.
    
    Closes: #142

 gnomemusic/views/baseview.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gnomemusic/views/baseview.py b/gnomemusic/views/baseview.py
index 8c1d5b1..fb14d70 100644
--- a/gnomemusic/views/baseview.py
+++ b/gnomemusic/views/baseview.py
@@ -154,7 +154,7 @@ class BaseView(Gtk.Stack):
 
     @log
     def _on_cancel_button_clicked(self, button):
-        self._view.set_selection_mode(False)
+        self.unselect_all()
         self._header_bar.set_selection_mode(False)
 
     @log