Steps to Reproduce:
Enter The End
Build a tower out of a block that the Ender Dragon cannot break at x:0, z:0 (Above the middle of the bedrock perch)
Wait until the dragon enters the takeoff phase
Crash Report:
[media]
I'm finding it near impossible to recover from this w/o the use of external programs, so if you wish to try it, I don't recommend doing it on an important world that you aren't willing to loose!
Environment
OS: Ubuntu 15.10 (Linux 4.2.0 64-Bit)
Java: 1.8.0_111
JVM Args: -Xmx1G -Xms1G -XX:+UseG1GC
Looks like MC-88301 and MC-90423.
In general please attach the crash report instead of uploading it to a third party website.