Fix possible NPE in DialerDatabaseHelper

In certain cases (third party contact backup solutions?) it is possible
for raw contacts to end up with null display names, which the Dialer
was crashing on. This fix performs a null check and inserts the default
(No name) contact name if we find that the display name is null.

Bug: 11750613
Change-Id: Ifbaf2861534e6eaf8a86d50d584d11a9fa38b65f
Merge tag 'android-sdk-4.4.2_r1' of https://android.googlesource.com/platform/packages/apps/Dialer into cm-11.0_test

Android SDK 4.4.2 Release 1