feat: checking whether contract exists when getting storage (#1296)

# Description

Fixes #1228 

# Checklist:

- [ ] I have reviewed my diff in github, line by line.
- [ ] Every change is related to the PR description.
- [ ] I have
[linked](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)
this pull request to the issue(s) that it resolves.
- [ ] There are no unexpected formatting changes, superfluous debug
logs, or commented-out code.
- [ ] The branch has been merged or rebased against the head of its
merge target.
- [ ] I'm happy for the PR to be merged at the reviewer's next
convenience.

yarn-project/aztec-rpc/src/aztec_rpc_server/aztec_rpc_server.test.ts

@@ -58,4 +58,11 @@ describe('AztecRpcServer', function () {
       rpcServer.addAccount(await keyPair.getPrivateKey(), address, partialAddress),
     ).rejects.toThrow(`Account ${address} already exists`);
   });
+
+  it('throws when getting public storage for non-existent contract', async () => {
+    const contract = AztecAddress.random();
+    await expect(async () => await rpcServer.getPublicStorageAt(contract, new Fr(0n))).rejects.toThrow(
+      `Contract ${contract.toString()} is not deployed`,
+    );
+  });
 });

yarn-project/aztec-rpc/src/aztec_rpc_server/aztec_rpc_server.ts

@@ -206,6 +206,9 @@ export class AztecRPCServer implements AztecRPC {
    * @returns A promise that resolves to an array of note preimage items, each containing its value.
    */
   public async getPublicStorageAt(contract: AztecAddress, storageSlot: Fr) {
+    if (!(await this.isContractDeployed(contract))) {
+      throw new Error(`Contract ${contract.toString()} is not deployed`);
+    }
     return await this.node.getStorageAt(contract, storageSlot.value);
   }