uniprop, for Bidi_Mirroring_Glyph return empty string if no BMG
uniprop, for Bidi_Mirroring_Glyph return empty string if no BMG

Before we would return a U+0000 character; returning an empty string is
will evaluate as Falsey, unlike a U+0000 in a string.

tbrowder/rakudo,salortiz/rakudo,jonathanstowe/rakudo,tony-o/rakudo,raydiak/rakudo,raydiak/rakudo,salortiz/rakudo,softmoth/rakudo,sjn/rakudo,nbrown/rakudo,Gnouc/rakudo,labster/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,nbrown/rakudo,sjn/rakudo,samcv/rakudo,labster/rakudo,tony-o/rakudo,nbrown/rakudo,tony-o/rakudo,usev6/rakudo,rakudo/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,nbrown/rakudo,rakudo/rakudo,salortiz/rakudo,raydiak/rakudo,softmoth/rakudo,jonathanstowe/rakudo,rakudo/rakudo,usev6/rakudo,lucasbuchala/rakudo,lucasbuchala/rakudo,salortiz/rakudo,rakudo/rakudo,labster/rakudo,Gnouc/rakudo,jonathanstowe/rakudo,usev6/rakudo,jonathanstowe/rakudo,samcv/rakudo,MasterDuke17/rakudo,samcv/rakudo,samcv/rakudo,nbrown/rakudo,softmoth/rakudo,tbrowder/rakudo,salortiz/rakudo,Gnouc/rakudo,labster/rakudo,awwaiid/rakudo,jonathanstowe/rakudo,rakudo/rakudo,tbrowder/rakudo,labster/rakudo,sjn/rakudo,lucasbuchala/rakudo,sjn/rakudo,tony-o/rakudo,usev6/rakudo,MasterDuke17/rakudo,awwaiid/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,sjn/rakudo,samcv/rakudo,tbrowder/rakudo,awwaiid/rakudo,Gnouc/rakudo,tony-o/rakudo,raydiak/rakudo,rakudo/rakudo,MasterDuke17/rakudo,softmoth/rakudo,nbrown/rakudo,Gnouc/rakudo,labster/rakudo,usev6/rakudo,softmoth/rakudo,awwaiid/rakudo,MasterDuke17/rakudo,awwaiid/rakudo,MasterDuke17/rakudo,salortiz/rakudo