Allow blank values to be stored in reactive cache

What does this MR do?

The reactive caching concern was using .present? to determine if it got a valid value from the cache. .present? returns false for values such as false, [], {}. Change this check to !.nil? instead so that such values can also be stored in cache.

What are the relevant issue numbers?

#56851 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer