rtf formatter crash on "exotic" fonts

[alessandrobelli]

There was a crash on this line, in the file State.php:

$font = self::$fonttbl[$this->font];

To trace the problem, we can go into LoadFont and ExtractFontTable in HtmlFormatter.php. Somehow the way rtf is setting the non-common font is not included in this formatter.
To avoid the crash, I changed this:

    if(isset($this->font) {
      $font = self::$fonttbl[$this->font];
      $style .= $font->toStyle();
    }

to

    if(isset($this->font) && count( self::$fonttbl)>0) {
      $font = self::$fonttbl[$this->font];
      $style .= $font->toStyle();
    }

The result is the document without the "exotic" font.