fix(block): fix crash on empty right aligned title (#933)

- Simplified implementation of the rendering for block.
- Introduces a subtle rendering change where centered titles that are
  odd in length will now be rendered one character to the left compared
  to before. This aligns with other places that we render centered text
  and is a more consistent behavior. See
  #807 (comment)
  for another example of this.

Fixes: #929