Document No hosts matched the subscripted pattern

Fixes: ansible#2422

src/ansiblelint/_internal/internal_error.md

@@ -31,3 +31,13 @@ them to the `exclude_paths`.
   hosts: localhost
   tasks: []
 ```
+
+## ERROR! No hosts matched the subscripted pattern
+
+If you see this error, it means that you tried to index a host group variable
+that is using an index above its size.
+
+Instead of doing something like `hosts: all[1]` which assumes that you have
+at least two hosts in your current inventory, you better write something like
+`hosts: "{{ all[1] | default([]) }}`, which is safe and do not produce runtime
+errors. Use safe fallbacks to make your code more resilient.