Fix crash when closing tab then doing tab-focus-last.

qutebrowser/browser/commands.py

@@ -572,6 +572,8 @@ class CommandDispatcher:
     @cmdutils.register(instance='mainwindow.tabs.cmd')
     def tab_focus_last(self):
         """Select the tab which was last focused."""
+        if self._tabs.last_focused is None:
+            raise CommandError("No last focused tab!")
         idx = self._tabs.indexOf(self._tabs.last_focused)
         if idx == -1:
             raise CommandError("Last focused tab vanished!")

qutebrowser/widgets/tabbedbrowser.py

@@ -268,6 +268,10 @@ class TabbedBrowser(TabWidget):
             tab = self.widget(idx)
             if tab is None:
                 raise ValueError("invalid index {}!".format(idx))
+        if tab is self.now_focused:
+            self.now_focused = None
+        if tab is self.last_focused:
+            self.last_focused = None
         last_close = config.get('tabbar', 'last-close')
         if self.count() > 1:
             url = tab.url()