Avoid NoSuchElementException "No value present"

When parsing the response from Cache#getIfPresent we end up in states
where EiffelEventIdCache#getEventIdIfPresent throws
NoSuchElementException.
Rewrite the conversion from @Nullable Optional<UUID> to Optional<UUID>
to be more clear to avoid this or at least get a clear indication of
exactly what happens.

Solves: Jira GER-1612
Change-Id: I3668c29aa284674a0cf8e36be80162f4d1bf71eb