Dialer: Hide "Add 2-sec pause" and "Add wait" if phone number is empty

There is no operation to hide "Add 2-sec pause" and
"Add wait" options.

When the phone number is empty, hide "Add 2-sec
pause" and "Add wait" options.

CRs-Fixed: 537440

Change-Id: Ia799e11808e57919f471437021e7d6d62edea07c