Missing snippet input results in deactivated "Save" button

Created by: Razer6

When creating a new snippet with missing title or filename the "Save" button gets deactivated. There no editing is possible anymore and the snippet must be truncated.

Steps to reproduce:

• Go to http://demo.gitlabhq.com/diaspora/diaspora/snippets
• Create a new snippet WITHOUT title or filename
• Press save

Result: Nothing happens. The save button is deactivated so you can't edit the snippet and save it again.

Expected behavior: An error message that some required input is missing.

Confirmed on: c8ba5c2d