Follow-up from "Fix view wiki pages that contain empty spaces in their file names"

The following discussion from !135626 (merged) should be addressed:

• @engwan started a discussion:

  I see NoMethodError failures in the logs because matched_files can return false.

  See https://nonprod-log.gitlab.net/app/discover#/doc/ed942d00-5186-11ea-ad8a-f3610a492295/pubsub-rails-inf-gstg-001712?id=qM1ID5AB7UTw2XCLwX72

  Maybe we still need the return if matched_files.blank? early return to handle this case?

  cc @kassio