Don't stop processing changesets if there is an error

I couldn't reproduce #1895, so i looked at the changes that were made before the release of 1.2.11 and noticed that we had just introduced the changeset queue..

There are multiple places in the code processing the changesets where an error halts the current's pad's queue, because the queue callback isn't called. So, I fixed that and ask @rchllc and @ldidry to test this branch (`git pull origin && git checkout fix/handle-message-continuation`)