Handle 'IndexOutOfBoundsException' when mod-pubsub try to register new modules

Steps to Reproduce:

1. Set up vagrant box locally (via 'vagrant up')
2. Get logs from 'mod-pubsub'
3. Create new RMB-based modules which have 'MessagingDescriptior'-file with the configuration for publisher and subscriber.
4. Run 'run-basic.sh' script for adding these new modules
5. Get logs from 'mod-pubsub'

Expected Results:
Logs should have information about successfully registration for new modules

Actual Results:
'IndexOutOfBoundsException' in MessagingModuleDaoImpl:64 exists.

Add tests in pub-sub client

Note: It seems that the main cause is that we have an empty 'publications' or 'subscriptions' arrays in modules.