Ive been having this problem with minecraft where im connected to the internet, but it wont let me on servers and when i try to get on to one it says, java,lang,NullPointerExeptaction: group. then when i try to get on single player, every time, i get kicked off minecraft

What I thought was going to happen was that I would open up minecraft. see that I could play online, then have a funky good glory time. but no.

What ACTUALY happened was this, I got on, I see that it says play offline and I say to myself, must be a bug, I start to "Play Oflline" and try to get into a server and I am met with a big Error: java,lang,NullPointerExeptaction: group
Then I say well that's odd, so I try my singleplayer world and I get kicked of of minecraft, I try the same thing 4 times and each time it kicked me off.
Im Flustered.

Steps to Reproduce:
1. Has me offline, when im online
2. go to Server
3. Get error
Or on singleplayer Error
1.Get offline, even when your connected.
2. Go to singleplayer world
3. Get kicked off of minecraft...