metadump: don't crash if client lost
metadump: don't crash if client lost

fixes previous commit :|

gencer/memcached,gencer/memcached,memcached/memcached,dormando/memcached,gencer/memcached,memcached/memcached,gencer/memcached,dormando/memcached,memcached/memcached,memcached/memcached,dormando/memcached,dormando/memcached,memcached/memcached,dormando/memcached,gencer/memcached