Fix NPE when processing connection status event with ECU

[kaushalaroraharman]

Resolves #37

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Describe behaviour before the change

• Stream base throwing error while processing subscribe/unsubscribe events from the device without the property dma.dispatcher.ecu.types

Describe behaviour after the change

• ECU type list has been initialized with an empty list, in case no ecus are defined in configuration to avoid NPE.

Pull request checklist

• I have read the CONTRIBUTING.md
• My code follows the code style of this project
• Tests for the changes have been added (for bug fixes / features)
• All new and existing tests passed.
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

• Yes
• No

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud