Check for empty lookup keys in getLookupUri

        /**

         * Build a {@link #CONTENT_LOOKUP_URI} lookup {@link Uri} using the

         * given {@link ContactsContract.Contacts#_ID} and {@link #LOOKUP_KEY}.

         * <p>

         * Returns null if unable to construct a valid lookup URI from the

         * provided parameters.

         */

        public static Uri getLookupUri(long contactId, String lookupKey) {

            if (TextUtils.isEmpty(lookupKey)) {

                return null;

            }

            return ContentUris.withAppendedId(Uri.withAppendedPath(Contacts.CONTENT_LOOKUP_URI,

                    lookupKey), contactId);

        }