Log cruft: anonymous requests to Fisheye pages generate errors and warnings

Some projects on studio.atlassian.com are anonymously viewable, eg:

https://studio.atlassian.com/source/browse/PL

Any anonymous fisheye request triggers 2 errors and a warning:

@4000000048299c2232ab273c 2008-05-13 06:48:08,849 TP-Processor7 ERROR [crowd.integration.osuser.CrowdCredentialsProvider] Failed to find user:
@4000000048299c223625d2f4 2008-05-13 06:48:08,895 TP-Processor7 WARN [atlassian.seraph.filter.TrustedApplicationsFilter] User '' referenced by trusted application: '7F0000010118BB283252456900E1E2B3' is not found.
@4000000048299c23087978c4 2008-05-13 06:48:09,138 TP-Processor18 ERROR [crowd.integration.osuser.CrowdCredentialsProvider] Failed to find user:
@4000000048299c23090b4ccc 2008-05-13 06:48:09,147 TP-Processor18 WARN [atlassian.seraph.filter.TrustedApplicationsFilter] User '' referenced by trusted application: '7F0000010118BB283252456900E1E2B3' is not found.

This means that when a crawler finds Fisheye and starts trying to index it, we get thousands of errors and warnings appearing in the logs.