BUG: update CTK with dicom fix

Exceptions thrown from ctk could cause spurious
errors, for example when checking for extensions.
This fix causes CTK to always return a usable
result to no error checking is needed in slicer.

https://github.com/commontk/CTK/issues/706

From: Steve Pieper <pieper@isomics.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25893 3bd1e089-480b-0410-8dfb-8563597acbee