Fix memory bug
Fix memory bug

The test suite would segfault once every 20-25 times... not anymore! I've never
seen this when actually using byebug but this might be related to the "random
crashes" I've heard of.

icebreaker/byebug,davidmowrer/in_class_projects_t2,phusion/byebug,scalp42/byebug,saisai/byebug,guilherme/byebug,yui-knk/byebug,webdev1001/byebug,ozydingo/byebug,saisai/byebug,k0kubun/byebug,guilherme/byebug,miamiruby/byebug,deivid-rodriguez/byebug,deivid-rodriguez/byebug,miamiruby/byebug,edward/byebug,davidmowrer/in_class_projects_t2,ozydingo/byebug,davidmowrer/in_class_projects_t2,os97673/byebug,guilherme/byebug,webdev1001/byebug,phusion/byebug,os97673/byebug,k0kubun/byebug,deivid-rodriguez/byebug,yui-knk/byebug,icebreaker/byebug,edward/byebug,k0kubun/byebug,scalp42/byebug,yui-knk/byebug