check for pastLogs.length before continuing in subscribeToBatchPublications

[shannonwells]

Problem

In subscribeToBatchPublications, we needed to check the length of pastLogs before trying to look at the blockNumber of one of its elements. Fixes #179033826

Solution

Do the length check Add a regression test that shows the red/green behavior

Double Checks:

• [x] Did you update the changelog?

Steps to Verify:

1. The test passes
2. For extra credit you can build sdk and make example-client use it, then launch a hardhat localnet with no logs or anything, and login to the example client. You should not see the error message as shown in the Tracker story.