I dont know how to recreate playing on a 14w18a server client crash playing on a map generated in 1.7 all portals tested before update

tested with other people and portals about 60% of the time it crashes with certain portals with the portals that crash people it crashes all people tested who went though the certain portals on reconnect shows world for about 2 seconds and then crashes again with the same error report

The error report
http://pastebin.com/a5D13BAT