Don't show afw default app pref if there is no candidate.

Change-Id: I25f077662264406a8a4d819db7b4713be753a33b
Fix: 22564285
Test: make RunSettingsRoboTests

src/com/android/settings/applications/defaultapps/DefaultPhonePreferenceController.java

@@ -42,7 +42,11 @@ public class DefaultPhonePreferenceController extends DefaultAppPreferenceContro
         final boolean hasUserRestriction =
                 um.hasUserRestriction(UserManager.DISALLOW_OUTGOING_CALLS);
 
-        return !hasUserRestriction;
+        if (hasUserRestriction) {
+            return false;
+        }
+        final List<String> candidates = getCandidates();
+        return candidates != null && !candidates.isEmpty();
     }
 
     @Override
@@ -60,6 +64,10 @@ public class DefaultPhonePreferenceController extends DefaultAppPreferenceContro
         }
     }
 
+    private List<String> getCandidates() {
+        return DefaultDialerManager.getInstalledDialerApplications(mContext, mUserId);
+    }
+
     public static boolean hasPhonePreference(String pkg, Context context) {
         List<String> dialerPackages =
                 DefaultDialerManager.getInstalledDialerApplications(context, UserHandle.myUserId());