default to empty string for notifications that didn't include content.
default to empty string for notifications that didn't include content.

show "" isntead of "undefined" for notifications that didn't include
content previously

nekodex/osu-web,LiquidPL/osu-web,notbakaneko/osu-web,nanaya/osu-web,notbakaneko/osu-web,ppy/osu-web,ppy/osu-web,LiquidPL/osu-web,nanaya/osu-web,nanaya/osu-web,ppy/osu-web,nekodex/osu-web,ppy/osu-web,notbakaneko/osu-web,omkelderman/osu-web,notbakaneko/osu-web,nekodex/osu-web,nanaya/osu-web,LiquidPL/osu-web,LiquidPL/osu-web,omkelderman/osu-web,omkelderman/osu-web,LiquidPL/osu-web,nekodex/osu-web,omkelderman/osu-web,nekodex/osu-web,ppy/osu-web,notbakaneko/osu-web,nanaya/osu-web