Fix sliceViewer

[rolanddenis]

PR Description

Fixing sliceViewer bug that cause assert failure and exception raise when the imported image domain doesn't contain the (0,0,0) point (like the example file provided in #255).

Checklist

• [N/A] Doxygen documentation of the code completed (classes, methods, types, members...)
• [N/A] Check if it follows the tools structure described in CONTRIBUTING.md
• New entry in the ChangeLog.md added.
• [N/A] Update the readme with potentially a screenshot of the tools if it applies.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).

[kerautret]

Nice, thanks a lot @rolanddenis , works fine now ;) !
Just waiting AppVeyor and merging