whenever i try to log on to minecraft it crashes. the same thing happened with my sister when she tried logging on. Can you please fix it?

Put the summary of the bug you're having here

*What I expected to happen was I logged on into Minecraft and then went into Vinella Verse and it logged me out and gave me a crash report

what should happened was me not getting logged out. I was doing things as I do every other day and it has NEVER logged me out.

*What actually happened was I went in to Vinella Verse, I started to walk, and then I got logged out.
The same thing happened as I said up there ^

Steps to Reproduce:
1. Log on to Minecraft
2. go onto Vinella Verse
3. Walk around and then it logs you out.