Fix Publikator Crashing on Extra Title Content

[jstcki]

When extra paragraphs are in the title section (e.g. when adding one through editing the source), normalization tries to unwrap extra nodes which results in a invalid document that throws the editor into an infinite loop.

Removing extra nodes solves this. However, content (e.g. a valid credits paragraph) will be lost. Maybe there's a better solution like removing extra paragraphs before the last one.