audiopolicy: Fix crash in getMsdPatches

Added a missing check for the possibility of not having an MSD module.
Remove a check for the module handle, as mHwModules by design
can't contain modules with AUDIO_MODULE_HANDLE_NONE (see
AudioPolicyManager::initialize).

Bug: 117253728
Test: see the repro steps in the bug
Change-Id: Ia8761a2e3ceccf9595b672c8ba48e086b457e3ae