fixed bug with no property

if node has no property with given name structure says no property on website.
fixed with default-value != null in content-types:

- [ ] test coverage
- [ ] finish the code
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation


| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/sulu-cmf/sulu/issues/32
| Doc           | none