`appstreamcli` Must Not Validate the Existance of Standard Icon Names

[JakeSmarter]

Standard icon names in icon elements of type="stock" must not be validated for existence. They are assumed to exist by definition. Validation of standard icon names may fail with an error in build environments that lack a desktop environment installed and yet are valid values for icons of type="stock", no matter if they exist or not. In other words, appstreamcli returns an error if it cannot find (or resolve) a stock icon name to a physical file. If anything, appstreamcli should report a warning if it cannot find a standard icon name, but no more.

[ximion]

We actually had that debate very briefly when that warning was introduced. And we do want the stock icons to be available in some form, and since they are installed with the app usually, we unconditionally check for them.
So far, this has not caused any issues.

Which app/stock-icon combination is causing problems in this case?