message: [Truffle-v5] Fix to optional
diff: @@ -95,8 +95,8 @@ declare namespace Truffle {
  contract: any
  transactionHash: string
  abi: AbiItem[]
  - allEvents(params: EventOptions): EventEmitter
  - send(value: BN | string, txParams: TransactionConfig): PromiEvent<TransactionReceipt | TransactionRevertInstructionError>
  + allEvents(params?: EventOptions): EventEmitter
  + send(value: BN | string, txParams?: TransactionConfig): PromiEvent<TransactionReceipt | TransactionRevertInstructionError>
  sendTransaction(transactionConfig: TransactionConfig): PromiEvent<TransactionReceipt | TransactionRevertInstructionError>
  }
  