Fix NPE for details number

The phone number can be null in the call log (typically for conference calls),
but this wasn't handled properly for calls from non-contacts.

This CL fixes the issue by instead using the display number. PhoneNumberUtils
properly handles null values and can parse the formatted version.

Bug: 77486039
Test: manual :/
PiperOrigin-RevId: 191492307
Change-Id: I1be427b3f4ed1381bea3943d130256618f730f5d