When using a derived loader I get a confusing error. My basic setup is this:

// SCHEMA
type Pool {
  # `Pool-${token0.toHexString()}-${token1.toHexString()}`
  id: ID!
  stakingPool: StakingPool
}
type StakingPool {
  id: Bytes!
  liquidityPool: Pool!
}

// WHEN ADDING THE POOL FIRST
poolEntity.stakingPool = idOfFutureStakingPool;


const stakingPool = StakingPool.load(poolAddress)!;
const lp = stakingPool.liquidityPool.load()[0];

The last line is crashing with the error:
Mapping aborted at ~lib/@graphprotocol/graph-ts/common/value.ts, line 80, column 5, with message: Value is not a string.

What am I doing wrong? I didn’t find any documentation for this modifier or any other for the subgraph. Also if I did anything wrong shouldn’t the loader return an empty array instead of exploding in my face?

Using the derived field works well (in inspecting the store) but using the loader doesn’t.