BluetoothDevice#getUuids() returns null again when no Uuids

getUuids was wrongly returning an empty array of Uuids when
fetchUuidsWithSdp had not been called. It now returns null
again.

Test: atest CtsBluetoothTestCases
Bug: 235456437
Tag: #feature
Ignore-AOSP-First: will be cherry-picked
Change-Id: If8aafc1b0ab4e253fdacc827726d76825b3bd1e4