message: Fix serialiser assert firing when writing structured chunk data
diff: @@ -593,7 +593,9 @@ void Serialiser<SerialiserMode::Writing>::WriteStructuredFile(const SDFile &file
  scratchWriter.m_ChunkFlags = m_ChunkFlags;
  }
  - ser->BeginChunk(m_ChunkMetadata.chunkID, m_ChunkMetadata.length);
  + m_ChunkMetadata.chunkID = 0;
  +
  + ser->BeginChunk(chunk.metadata.chunkID, m_ChunkMetadata.length);
  if(chunk.metadata.flags & SDChunkFlags::OpaqueChunk)
  {
  