printallheaders=##t outputs the title twice, if no title is specified within the score section

[Claus Tirel]

> I'm not top posting.

printallheaders=##t results in a double output of the main title, if no title is
specified within the score section.

============= begin example.ly =============
\version "2.8.1"
\paper{
  printallheaders=##t
}
\header{
  title = "Title"
}
\score{
  \relative c'{
    c 
  }
}
============= end example.ly =============