fix NoneType exception on timeincrement

[Rdornier]

Fixes #606

Added a None check in that line

[will-moore]

Thanks for the report and fix.
I can't seem to reproduce this on any images I've tested with (I can't even set the timeIncrement value to None on a test image using example at https://forum.image.sc/t/how-to-correctly-set-a-timeincrement-for-omero-pixels/101600).
Do you see this on all time-lapse images?

However, the fix looks like the right fix for this error, so I'm happy to approve...

[will-moore]

Deployed on merge-ci and tested loading various time-lapse images. Images and Timestamps loading without errors.

[will-moore]

Released as omero-figure 7.2.1

[Rdornier]

Thanks a lot for the quick merge & release, Will !

Do you see this on all time-lapse images?

No, only on specific images coming from an Incucyte microscope.

I can't seem to reproduce this on any images I've tested with

I cannot share the problematic data. However, if you create a timelapse image on Fiji, you can get the same error.
Here is a dummy timelapse timelapse-test.zip that should produce the bug.