Change multi-day event to a single day event.

1) Use the month view on demo calander.
2) Click on the 'Zk Spreadsheet 1.0.0 RC2 Release' event.
3) Change EndDate to July 8, 2015 and Time to 9:30.
4) Click 'Ok'.
Then get the error:
Failed to process
setAttr
Unable to get property 'getTime' of undefined or null reference
(TypeError)

The error also occurs if you change a single day event to a multi-day event.