metaplex.rpc().getAssetsByOwner() returns an error, but my RPC supports compressed NFTs when not using Metaplex

[mikemaccana]

May be related to #514 as I can't find any documentation on metaplex.nft().

const assetListOrError = await metaplex.rpc().getAssetsByOwner({
  ownerAddress: publicKey.toBase58(),
});

(wallet address is my own 5FHwkrdxntdK24hgQU8qgBjn35Y1zwhz1GZwCkP2UJnM)

Returns:

{
  "name": "RpcError",
  "source": "rpc"
}

However my RPC supports supports compressed NFTs and works fine when using the code from https://github.com/solana-developers/compressed-nfts:

const response = await connection.getAssetsByOwner({
  ownerAddress: publicKey.toBase58(),
});