message: change storage to return none for network requests where block(header) has no signatures
diff: @@ -602,8 +602,14 @@ impl Storage {
  let item_id = decode_item_id::<BlockWithMetadata>(serialized_id)?;
  let opt_item = self
  .read_block_and_metadata_by_height(item_id)
  - .map_err(FatalStorageError::from)?;
  - // TODO: At least one signature?
  + .map_err(FatalStorageError::from)?
  + .and_then(|block_with_metadata| {
  + if block_with_metadata.finality_signatures.proofs.is_empty() {
  + None
  + } else {
  + Some(block_with_metadata)
  + }
  + });
  Ok(self.update_pool_and_send(
  effect_builder,
  @@ -631,8 +637,18 @@ impl Storage {
  let item_id = decode_item_id::<BlockHeaderWithMetadata>(serialized_id)?;
  let opt_item = self
  .read_block_header_and_metadata_by_height(item_id)
  - .map_err(FatalStorageError::from)?;
  - // TODO: At least one signature?
  + .map_err(FatalStorageError::from)?
  + .and_then(|block_header_with_metadata| {
  + if block_header_with_metadata
  + .block_signatures
  + .proofs
  + .is_empty()
  + {
  + None
  + } else {
  + Some(block_header_with_metadata)
  + }
  + });
  Ok(self.update_pool_and_send(
  effect_builder,
  