Robot Framework: misleading warning message

When running a successful Robot Framework test (here https://gitlab.com/lmazure_TestGroup/robotframeworkstringtest/-/blob/main/case.robot?ref_type=heads), we get this warning message:

This message is indicated because there is no *-attachment.html file. But this is a common situation: *-attachment.html files seem to be created only when an error (e.g. a non-existing step) occurs or when a variable is set.

We should be silent when there is no *-attachment.html file to get. (If allure-robotframework is missing, a message will still be displayed when trying to get the *-result.json files:
)