When rendering missing or redundant patterns, linked-list would
wrongly suggest the last nil constructor as a pattern on non-empty
list.
For example, before this commit, the exhaustivness checker would yield:
```
[(_, True), []]
```
as a suggestion, for being the result of being a list pattern with a
single argument being `(_, True) :: Nil`. Blindly following the
compiler suggestion here would cause a type unification error (since
`[]` doesn't unify with a 2-tuple).
Indeed, we mustn't render the Nil constructor when rendering non-empty
lists! So the correct suggestion should be:
```
[(_, True)]
```
rvcas