handle orphaned taxonomy lines
handle orphaned taxonomy lines

Replace a perl error message with a human one.
"Use of uninitialized value $canon_tagid in hash element at lib/ProductOpener/Tags.pm line 1324, <$IN> line 14732." =
"taxonomy : ingredients : discarding orphan line : description : ..."

Deliberately discard lines rather than accidentally discarding them by overwriting the same empty variable each time.

openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server