Fix null pointer in dashboard fragment test.

- use context instead of activity to retrieve resource details.
- revert the change previously made in getActivity() calls.
- add null checking in package name and tile intent.

Fix: 34396855
Test: make RunSettingsRoboTests

Change-Id: Ic853939fee3c381b663c0320354da51d3b2a0e11

tests/robotests/src/com/android/settings/dashboard/DashboardFragmentTest.java

@@ -79,6 +79,7 @@ public class DashboardFragmentTest {
         when(mFakeFeatureFactory.dashboardFeatureProvider.getTilesForCategory(anyString()))
                 .thenReturn(mDashboardCategory);
         mTestFragment.onAttach(ShadowApplication.getInstance().getApplicationContext());
+        when(mContext.getPackageName()).thenReturn("TestPackage");
     }
 
     @Test