BUG: Clearing vector instead of list in MarkDuplicateFramesInvalidImageFilter.

The clear resized the vector to 0 when the intention is to clear the contents of
the containter at that vector element.

Detected by the Visual Studio test failures.

Change-Id: I99294fff503386e7971f75e6d9cb3505f6ee948e
Merge pull request #208 from thewtex/duplicate-clear

BUG: Clearing vector instead of list in MarkDuplicateFramesInvalidImageF...