ISS' processCommitted may delete a delivered certificate without sending the DeliverCert event

[ranchalp]

The solution should be simply replacing:

var cert availabilitypb.Cert
		if len(certData) > 0 {
			if err := proto.Unmarshal(certData, &cert); err != nil {
				return nil, fmt.Errorf("cannot unmarshal availability certificate: %w", err)
			}
		}

by

var cert availabilitypb.Cert
		if len(certData) > 0 {
			if err := proto.Unmarshal(certData, &cert); err != nil {
				return eventsOut, fmt.Errorf("cannot unmarshal availability certificate: %w", err)
			}
		}

But TBD. Also I am currently updating the module to use the DSL, hence making a DSL-compatible solution.