fetchContractDataMapEntry fails with JSON error

[dantrevino]

  const lookup_key = { "key": cvToHex(uintCV(asset_id)) }
  
  const mapEntry = await fetchContractDataMapEntry({
    url: network.getCoreApiUrl(),
    contract_name,
    contract_address,
    map_name,
    lookup_key
  });

fails with SyntaxError: Unexpected end of JSON input at line 0, col 0

Not sure if this is my lookup_key, but it appears that the body being sent to the api is not being set as application/json.

micro-stacks/src/api/smartcontracts/fetchers.ts

Lines 108 to 113 in 2ba20d8

	const body = lookup_key;
	const path = generateUrl(
	`${v2Endpoint(url)}/map_entry/${contract_address}/${contract_name}/${map_name}`,
	{ proof: proof, tip: tip }
	);
	return fetchJsonPost<MapEntryResponse>(path, { body });