Bug#529976: 'support_zipped = true' breaks texdoc

[أحمد المحمودي <aelmahmoudy@users.sourceforge.net>]

Hello,

  I have edited /usr/bin/texdoc to change support_zipped value to true, 
  yet that broke texdoc. When I run:

  texdoc pgfmanual
  
  I get this:

  /usr/bin/texdoc:621: attempt to concatenate global 'zipext' (a nil 
  value)

  The same if I run: texdoc url

  which used to work before changing support_zipped value.

-- 
 ‎أحمد المحمودي (Ahmed El-Mahmoudy)
  Digital design engineer
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