Fix createLaunchEmergencyDialerIntent API behavior when Telecom unavailable.

The API contract for createLaunchEmergencyDialerIntent indicates that
the return value is @NonNull, however the code clearly can return a null
value if either:
1. Telecom is unavailable.
2. There is a remote exception.

Since the API just returns a new ACTION_EMERGENCY_DIAL intent with the
package name of the emergency dialer (from Telecom string resources), we
can provide a reasonable fallback behavior by just returning a new
ACTION_EMERGENCY_DIAL intent with no targeted package.  The system will
still launch the emergency dialer in this case, but if there is a scenario
where multiple emergency dialers are installed on a device, the AOSP one
may get launched instead.  This is, however, better than there being NO
emergency dialer launched.

Test: Comment out call to Telecom service and verify the AOSP emergency
dialer still launches.
Fixes: 152187752

Change-Id: I06f8a5bebace5b22822f7bb714e14915126b904f