No ref for opencat-docker by input parser: switch to master branch by default!

[ferishili]

It is implemented that we can now set a range of versions for moodle, php and opencast for action workflows to have them in matrix and generate the jobs, which is coming from config.json files in each plugin and gets parsed by the parse-matrix-action.

It appears that the index.js in parser would skip or does some faulty job, which in return gives back the opencast version as null or it does not exists at all. In result of that, what happen is, the ref for the action/checkout step when pulling the docker-opencast is going to be empty, and this will in return by default point to master branch, and at the time the master branch of docker-opencast is pointing to opencast 17 and the plugins are not compatible with that version.

As for a temporary fix I have provided a global input value to make sure that, when the parsed inputs have no opencast version ref, then use this global input: 0759e2a

This needs to be fixed in the https://github.com/Opencast-Moodle/moodle-workflows-opencast/blob/main/parse-matrix-action/index.js and my first assumption would be something in either the json parser for ocs or the loop