Add null check for actual date/time truncation

[papiomytoglou]

A missing null check in DateTimeTruncation#truncate results in null pointer exceptions whenever the user uses a matcher which includes truncateActual. This largely makes truncateActual unusable since it breaks functionality, especially when the mapping including truncateActual is added last.

References

Fixes #2466

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[oleg-nenashev]

Thanks! There is still an open issue with documentation/annotations and downstream use, but it definitely prevents NPE in this method. So it is net positive and should be merged IMO

[papiomytoglou]

Thank you for your response @oleg-nenashev. I'd gladly add any required documentation, it's just not clear to me what it should be since neither the signature nor the return value of the method were affected. If you could point me to any relevant guidelines I will amend the PR.

[oleg-nenashev]

@papiomytoglou Yes, this is actually the main problem. At the moment we do not have an agreed standard and guidelines on annotations, so it is not something one could address at the moment. Let's get it merged