highlight a possible Gtk bug in the code

This reverts commit 9b841df3e4.

src/mpdevil.py

@@ -2683,6 +2683,7 @@ class PlaylistWindow(Gtk.Overlay):
 		# connect
 		self._back_to_current_song_button.connect("clicked", self._on_back_to_current_song_button_clicked)
 		scroll.get_vadjustment().connect("value-changed", self._on_show_hide_back_button)
+		self._treeview.connect("notify::selected-path", self._on_show_hide_back_button)
 		settings.bind("mini-player", self, "no-show-all", Gio.SettingsBindFlags.GET)
 		settings.bind("mini-player", self, "visible", Gio.SettingsBindFlags.INVERT_BOOLEAN|Gio.SettingsBindFlags.GET)
 
@@ -2691,7 +2692,7 @@ class PlaylistWindow(Gtk.Overlay):
 		self.add_overlay(self._back_button_revealer)
 
 	def _on_show_hide_back_button(self, *args):
-		visible_range=self._treeview.get_visible_range()
+		visible_range=self._treeview.get_visible_range()  # not always accurate possibly due to a bug in Gtk
 		if visible_range is None or self._treeview.get_property("selected-path") is None:
 			self._back_button_revealer.set_reveal_child(False)
 		else: