Fix silent redial operation

When receiving handover state changed message,
the TelephonyConnection should be disconnected
if handover connection is null.

Test: atest CtsTelephonyTestCases

Change-Id: Iff31718f62e09ad99e4511e96842316b7c4f91c8
Signed-off-by: sung_jae <sung_jae.kim@samsung.com>
1 file changed