Endpoint irrelevant/file returns 500

Test have detected a case where the endpoint irrelevant/file responds with status code 500. It turned out that the predicate irrelevant/1 throws an exception. So the behavior of the WebAPI is correct.

Source of the exception is the predicate `manipulation_time/2'. When called with a directory as first argument the stored dict does not have the appropriate key. Thus an exception is thrown.

Evidence

• Failed tests: system_test:endpoint_irrelevant@file of job https://gitlab.rz.uni-bamberg.de/cogsys/dare2del/demonstrator/-/jobs/72393.
• Loaded background theory database
• Request body: {"abs_path": "dir_1/file_new"}

Tasks

• Refine the irrelevance_common.plt tests to catch this error in the future.
• Safeguard `manipulation_time/2' to fail when called with an directory at first argument.
• Test other irrelevance_common.pl predicates for similar errors.