Program crashes sometimes on global search

[Jesse Sloane]

Sometimes running a global search causes the program to crash, and the "Looks like you've found a bug" dialogue box appears.
In the most recent instance, the search string was a single string of latin letters.

--------------------------------------------------------
This is zim 0.65
Platform: nt
Locale: zh_CN cp1252
FS encoding: mbcs
Python: (2, 7, 11, 'final', 0)
Gtk: (2, 24, 10)
Pygtk: (2, 24, 0)
Zim revision is:
  branch: 065
  revision: 805 <email address hidden>
  date: 2015-11-01 15:42:45 +0100

======= Traceback =======
  File "zim\gui\searchdialog.pyo", line 92, in _search
  File "zim\gui\searchdialog.pyo", line 177, in search
  File "zim\search.pyo", line 254, in search
  File "zim\search.pyo", line 353, in _process_group
  File "zim\search.pyo", line 497, in _process_content
  File "zim\notebook.pyo", line 2011, in walk
  File "zim\index.pyo", line 1289, in _walk
  File "zim\index.pyo", line 1282, in _walk
InterfaceError: Error binding parameter 0 - probably unsupported type.