Solved Player name glitch

Some guy joined our server with a invisible name that you can see in the picture because i can't post the text here without being invisible.

http://image.prntscr.com/image/4a90542d5cbc467e9a8407acdedfd09e.png

Looks like this ingame:
https://i.gyazo.com/cffbc59d492fc9b35fb2e8b0e9d5a0ef.png

I just wanted you guys to know, so beware people!