Merge pull request #2214 from ethereum-optimism/sc/sdk-fix-no-batch

fix(sdk): correctly handle no batch case

.changeset/grumpy-ads-smile.md

+---
+'@eth-optimism/sdk': patch
+---
+
+Have SDK properly handle case when no batches are submitted yet

packages/sdk/src/cross-chain-messenger.ts

@@ -654,6 +654,11 @@ export class CrossChainMessenger implements ICrossChainMessenger {
     let batchEvent: ethers.Event | null =
       await this.getStateBatchAppendedEventByBatchIndex(upperBound)
 
+    // Only happens when no batches have been submitted yet.
+    if (batchEvent === null) {
+      return null
+    }
+
     if (isEventLo(batchEvent, transactionIndex)) {
       // Upper bound is too low, means this transaction doesn't have a corresponding state batch yet.
       return null