COMP: Clean up use of Dimensions in MetaImageIO.

For Coverity scan :

  CID 1081375 (#1 of 1): Uninitialized scalar variable (UNINIT)
  25. uninit_use_in_call: Using uninitialized value "*transformMatrix" when
  calling "MetaObject::TransformMatrix(double const *)".

Change-Id: I6b82c9b73f8aa52fc6e16604f9caf748c7384664
Merge topic 'coverity_merge1'

3bc1b8e COMP: Clean up use of Dimensions in MetaImageIO.