If no concept is selected to be downloaded to device, app crash happens when navigating to client summary's observations.

Steps to reproduce the crash

1. At the beginning of mUzima setup, select "patient data" as a configuration. press next.
2. After it finish the setup process, go to settings, then click Manage concepts to get more concepts.
3. Enter concept name (For example, weight)
4. Go back to the dashboard and enter Cohorts page, download the existing cohort again.
5. Go to Clients page, then select any client, then view observations.
6. When click on the observation to view summary's observations, the app will crash.