Fix typo serialization key in AbstractCinematicEven (Issue #2449)

[mondogo24]

As the issue #2449 stated. The serialization key, for the class's field initialDuration, should has been initialDuration but initalDuration was written. To fix it and, at the same time, avoid the backward incompatibility:

• In the write function: The key is always correctly setted as initialDuration.
• In the read function: First, it checks for initialDuration key, if not found, it uses the default value to indicate that it was not found. Then, the same it does with initalDuration. If none is found the class field initialDuration is set with the original default value, which is 10. I thought about using the value -1 as indicator of not finding the key since it shouldn't make sense negative temporal units for this field. Also added a commentary to indicate why a double check was occurring for future readers.

close #2449

[gemini-code-assist]

Code Review

This pull request corrects a typo in the serialization key for 'initialDuration' and implements backward compatibility to support the previous misspelled key 'initalDuration'. The review feedback suggests simplifying the fallback logic by nesting the read calls, which removes the need for magic numbers and improves code readability.

[riccardobl]

thank you!