Fix undefined method error when open block doesn't have a title
Fix undefined method error when open block doesn't have a title

asciidoctor/asciidoctor-latex,PissedCapslock/asciidoctor-latex,PissedCapslock/asciidoctor-latex,asciidoctor/asciidoctor-latex,PissedCapslock/asciidoctor-latex,jxxcarlson/asciidoctor-latex,jxxcarlson/asciidoctor-latex,jxxcarlson/asciidoctor-latex,asciidoctor/asciidoctor-latex