Fix potential NPE with Preference highlighting

- there are some cases where the ListView adapter is null

Change-Id: I9dcd171f57d9ca7b8032d890f5a18c3a01fd38cf

src/com/android/settings/SettingsPreferenceFragment.java

@@ -138,6 +138,7 @@ public class SettingsPreferenceFragment extends PreferenceFragment implements Di
 
     private int findPositionFromKey(String key) {
         final ListAdapter adapter = getListView().getAdapter();
+        if (adapter != null) {
             final int count = adapter.getCount();
             for (int n = 0; n < count; n++) {
                 Object item = adapter.getItem(n);
@@ -149,6 +150,7 @@ public class SettingsPreferenceFragment extends PreferenceFragment implements Di
                     }
                 }
             }
+        }
         return -1;
     }