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

Bug: 29421811
Change-Id: I0a73ba12bae4122f1d89fc92e5ea4f6a96cd1ed1

bool OMXCodec::drainAnyInputBuffer() {
 return drainInputBuffer((BufferInfo *)NULL);
}

bool OMXCodec::drainAnyInputBuffer() {
 return drainInputBuffer((BufferInfo *)NULL);
}
