split view figure z-projection with one z returns an error

[manics]

Discovered whilst creating a split-view-figure to test #159 on py3-ci

Select a multi-channel image with one Z. Create a split view figure, selection Z-projection. Run the script and you'll receive an error:

    serverExceptionClass = ome.conditions.ValidationException
    message = Z interval value cannot be >= 1

Expected behaviour: Should work, a maximum projection of an image with one Z should be the same as the original image. Alternatively disable the option.