Parser: Incorrect `Conditional element pattern detected`

Running `@herb-tools/linter` using `main`, we are now getting about a hundred invalid errors about conditional element patterns.

I was able to narrow it down to this failing example:

```html+erb
<% if true %>
  <% if true %>
    <div>
      <div></div>
      <% if true %><% end %>
    </div>
  <% else %>
    <div></div>
  <% end %>
<% end %>
```