[GeodesicSegmentation] Always demands .nii.gz or .nii output extension, even if it already is

[AlexanderGetka-cbica]

Describe the bug
No matter what you put for the output filename, GeodesicSegmentation complains that the output isn't in a NIfTI compatible format. You also can't just let it default -- -o is required.

To Reproduce
Steps to reproduce the behavior:

Run GeodesicSegmentation with any input (-i), any mask (-m), and specify any output (-o).
Ex: GeodesicSegmentation -i image.nii.gz -m mask.nii.gz -o output.nii.gz
See error message:
Output file extension needs to be compatible with NIfTI format. Only '.nii.gz' or '.nii' allowed

Try it again with anything as the output, it doesn't work.

Expected behavior
Run the algorithm if I have .nii or .nii.gz extension on my output.

CaPTk Version
1.8.1 release

Additional context
Seems to be coming from src/applications/GeodesicSegmentation.cxx line 293.
Check is:
if ((extension IS NOT .nii) OR (extension IS NOT .nii.gz)) -- this can never be false.