Warning for probably unintended category filter setting

[nji9]

If "Match mode" is set to OR:

If checking a filter for a category not set
while for another category filter is set already (or the other way round)
there might be given a warning/ notice,
as this might probably be an unintended match mode setting

... which gives wrong results (unnoticed?).

[nji9]

This suggestion holds even if my other suggestion
viewtopic.php?p=211416#p211416
should be realized.