Handle missing files more gracefully in "bup xstat".
Handle missing files more gracefully in "bup xstat".

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

ToxicFrog/bup,pombredanne/bup,apenwarr/bup,mhoeher/bup,gevaerts/bup,ToxicFrog/bup,mhoeher/bup,pombredanne/bup,mhoeher/bup,apenwarr/bup,ToxicFrog/bup,gevaerts/bup,pombredanne/bup,gevaerts/bup,apenwarr/bup,tjanez/bup,jbaber/bup,mhoeher/bup,jbaber/bup,ToxicFrog/bup,tjanez/bup,tjanez/bup,gevaerts/bup,jbaber/bup,tjanez/bup,pombredanne/bup,tjanez/bup,jbaber/bup,pombredanne/bup,pombredanne/bup,mhoeher/bup,ToxicFrog/bup,jbaber/bup,apenwarr/bup,jbaber/bup,gevaerts/bup,mhoeher/bup,tjanez/bup