Getting property on INTERFACE_LIBRARY targets fails

I have some code that walks through each link library of a target:

get_target_property(libraries ${_name] LINK_LIBRARIES)
foreach(lib ${libraries})
    get_target_property(config ${lib} CONFIG_FILE)
    if(config)
        # ...
    endif()
endforeach()

That works great. Except get_target_property, when called on an INTERFACE_LIBRARY, is a hard error:

INTERFACE_LIBRARY targets may only have whitelisted properties. The
property "CONFIG_FILE" is not allowed.

But I'm not trying to add a property, I'm trying to retrieve a property. Why not just return back an empty property instead? As a workaround, I first have to check the TYPE - which seems totally unnecessary. This is with cmake 3.10.