only try to switch pages in a notebook if we actually have one. Not a fix for, but somewhat workaround for the crashing aspect of LP #271850

terminatorlib/terminator.py

@@ -856,6 +856,7 @@ class Terminator:
 
   def previous_tab(self, term):
     notebook = self.get_first_parent_notebook(term)
+    if notebook:
       notebook.prev_page()
       # This seems to be required in some versions of (py)gtk.
       # Without it, the selection changes, but the displayed page doesn't change
@@ -864,6 +865,7 @@ class Terminator:
 
   def next_tab(self, term):
     notebook = self.get_first_parent_notebook(term)
+    if notebook:
       notebook.next_page()
       notebook.set_current_page(notebook.get_current_page())