With pathbar disabled, notebook may crash from resizing the window.

[K. Bauer]

==== How to reproduce the problem ====

1. Open at notebook.
2. Disable pathbar.
3. Make sure side bars are wider together than the minimum window
   width, i,e, the width of the menu bar.
4. Change the size of the window such that the central TextBuffer
   approaches zero width, either by resizing the Window dircectly or
   using features like Aero Snap ("maximize to half the screen").

==== Observed Behaviour ====

As the width of the TextBuffer approaches zero, ZIM hangs without any
further output to the console. Only force-killing the program helps
then.

==== Expected Behaviour ====

At some point the central TextBuffer should stop resizing, either
preventing resizing of the whole window or first force-resizing
sidebars.

If the pathbar is enabled the widest button (possibly one that isn't
even visible) determines the minimum width (which can be a problem in
itself when using long page names), but there seems to be no
limitation without a pathbar.

==== System Information ====
OS: Windows 7 64bit

------ Debug Output Header ------
INFO: Locale set to: en_US.cp1252
INFO: This is zim 0.60
DEBUG: Python version is sys.version_info(major=2, minor=7, micro=3, releaselevel='final', serial=0)
DEBUG: Platform is nt
DEBUG: Zim revision is:
  branch: pyzim-trunk
  revision: 672 <email address hidden>
  date: 2013-04-30 19:27:20 +0200

[Jaap Karssenberg (jaap.karssenberg)]

Will commit fix in rev710 of branch pyzim-refactor

Forced minimum size of 24 pixels.
To be tested on windows.

[Jaap Karssenberg (jaap.karssenberg)]

Fixed in release 0.61