BUG: Uninitialized value in VTKImageIOStreamTest

fixes: http://open.cdash.org/viewDynamicAnalysisFile.php?id=2989542

Change-Id: Ic28da21d4a22b9c005e0ea29298d7e7adf41d069
Merge topic 'streamingbug'

2189769 BUG: Uninitialized value in VTKImageIOStreamTest