Expected behavior
You can share by link using set default expiration date from the admin side.
When you click on share by link the expiration date is enable by default.
When you enforced expiration date, you can't select more days than it is shown by default but you can select less.
Actual behavior
You can share by link without knowing that there are an expiration date
And when you enable the option "Set expiry date", an error is shown:

Steps to reproduce
- Enable the option "Set default expiration date" from the admin side
- Try to share by link form the desktop
Client configuration
Version 1.8.0-nightly20150209(build2001)
Operating system: OS X 10.10.1