fix: staking-payouts for legacy kusama node

[TarikGul]

This resolves an error where legacy blocks on Kusama would throw an error:

{
	"code": 500,
	"message": "Cannot read properties of undefined (reading 'indexOf')",
	"stack": "TypeError: Cannot read properties of undefined (reading 'indexOf')\n    at AccountsStakingPayoutsService.deriveEraPayouts (/Users/tarikgul/Desktop/parity/tools-team/substrate-api-sidecar/src/services/accounts/AccountsStakingPayoutsService.ts:293:79)\n    at /Users/tarikgul/Desktop/parity/tools-team/substrate-api-sidecar/src/services/accounts/AccountsStakingPayoutsService.ts:170:50\n    at Array.map (<anonymous>)\n    at AccountsStakingPayoutsService.fetchAccountStakingPayout (/Users/tarikgul/Desktop/parity/tools-team/substrate-api-sidecar/src/services/accounts/AccountsStakingPayoutsService.ts:170:28)\n    at processTicksAndRejections (node:internal/process/task_queues:95:5)\n    at AccountsStakingPayoutsController.getStakingPayoutsByAccountId (/Users/tarikgul/Desktop/parity/tools-team/substrate-api-sidecar/src/controllers/accounts/AccountsStakingPayoutsController.ts:110:4)\n    at /Users/tarikgul/Desktop/parity/tools-team/substrate-api-sidecar/src/controllers/AbstractController.ts:116:5",
	"level": "error"
}

This fix checks to make sure validatorLedger.claimedRewards exists if not we continue with the rest of the logic.

We tested with: /accounts/FXCgfz7AzQA1fNaUqubSgXxGh77sjWVVkypgueWLmAcwv79/staking-payouts?unclaimedOnly=false&at=1567404&depth=21 and we got accurate results back.