DUI: hide little circle.

# Preface
Little circle between query and actions should be presented only when both of them are presented.
# Solution
I used MultiBinding.
# Before
![image](https://cloud.githubusercontent.com/assets/8158404/4488653/b7bb5e98-4a10-11e4-9bb7-8a9c4b7dac1f.png)
# After
![image](https://cloud.githubusercontent.com/assets/8158404/4488682/1f45c3c8-4a11-11e4-8f9e-7f5e26cacfdb.png)
# Reviewers
@Benglin,@vmoyseenko, please take a look.