Wireshark QMI dissector: bugfix in packet decoding

The Wireshark QMI dissector has a new commit to fix a bug when decoding packets for a service whose related structures are not declared.

Wireshark qmi

This could happen if the service was available in the services dictionary, but there was no related json file, preventing the service structures to be created. This is not unlikely: for example libqmi was missing QoS json until commit qos: new service.

The fix is to simply check that the needed structure has been declared before usage.

The Wireshark QMI dissector is available in github and, as usual, comments and contributions are welcome.