OMXCodec: check IMemory::pointer() before using allocation

Bug: 29421811
Change-Id: I0a73ba12bae4122f1d89fc92e5ea4f6a96cd1ed1

void OMXCodec::setState(State newState) {
    mState = newState;
    mAsyncCompletion.signal();

    mBufferFilled.signal();
}

void OMXCodec::setState(State newState) {
    mState = newState;
    mAsyncCompletion.signal();

    mBufferFilled.signal();
}
