Subgraph indexing error, mapping aborted with ethereum value is not an address

Subgraph indexing failing due to mapping abortion with reason – ethereum value is not an address, from one of the handlers. I understand the issue if from the handlePaymentExpenseCreated() function but I'm unable to pinpoint the issue. Everything seems right. Thank you in advance.
Here's the image of the logs.

The subgraph schema

type ActiveExpense @entity {
  id: ID!
  payer: Bytes!
  to: Bytes!
  splitBy: [Bytes!]!
  splitAmounts: [BigInt!]!
  expenseIndex: BigInt!
  blockTimestamp: BigInt!
  transactionHash: Bytes!
}

The mapping handler function

export function handlePaymentExpenseCreated(
  event: PaymentExpenseCreatedEvent
): void {
  const id: string = getIdFromParams(event.params.param0, event.params.param4);
  let activeExpense = ActiveExpense.load(id);
  let newExpense = new PaymentExpenseCreated(id);

  if (!activeExpense) {
    activeExpense = new ActiveExpense(id);
  }

  newExpense.payer = event.params.param0;
  activeExpense.payer = event.params.param0;

  newExpense.to = event.params.param1;
  activeExpense.to = event.params.param1;

  // two different methods of assinging type Address[] to type Bytes[]
  const splitAddresses = event.params.param2.map<Bytes>(
    (address: Bytes) => address
  );
  newExpense.splitBy = splitAddresses;
  activeExpense.splitBy = changetype<Bytes[]>(event.params.param2);

  newExpense.splitAmounts = event.params.param3;
  activeExpense.splitAmounts = event.params.param3;

  newExpense.expenseIndex = event.params.param4;
  activeExpense.expenseIndex = event.params.param4;

  newExpense.blockTimestamp = event.block.timestamp;
  activeExpense.blockTimestamp = event.block.timestamp;

  newExpense.transactionHash = event.transaction.hash;
  activeExpense.transactionHash = event.transaction.hash;

  newExpense.save();
  activeExpense.save();
}

Subgraph yaml file

specVersion: 0.0.5
schema:
  file: ./schema.graphql
dataSources:
  - kind: ethereum
    name: DeSplit
    network: goerli
    source:
      address: "0xA74c0C03A05B94a67FDc09351b312f122308335d"
      abi: DeSplit
      startBlock: 8402740
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.7
      language: wasm/assemblyscript
      entities:
        - ExpenseSettled
        - PaymentExpenseCreated
      abis:
        - name: DeSplit
          file: ./abis/DeSplit.json
      eventHandlers:
        - event: ExpenseSettled(address,address,uint256,uint256)
          handler: handleExpenseSettled
        - event: PaymentExpenseCreated(address,address,address[],uint256[],uint256)
          handler: handlePaymentExpenseCreated
      file: ./src/de-split.ts

The event emitted from the contract and link to the contract

emit PaymentExpenseCreated(
            msg.sender,
            _to, //address
            _splitBy, //address[]
            _splitAmount, // uint256[]
            expenses.length - 1 //uint256
        );

https://goerli.etherscan.io/address/0xA74c0C03A05B94a67FDc09351b312f122308335d