bundlerepo: avoid exception in __del__ when the bundle doesn't exist
$ hg -R bundle://foo.hg
abort: No such file or directory: foo.hg
Exception exceptions.AttributeError: "'bundlerepository' object has no attribute 'bundlefile'" in <bound method bundlerepository.__del__ of <mercurial.bundlerepo.bundlerepository object at 0xa7ab9fac>> ignored
abort: impossible time zone offset: 4444444
transaction abort!
rollback completed
abort: invalid date: '1\t15.1' see hg(1) manual page for details
transaction abort!
rollback completed
abort: invalid date: 'foo bar' see hg(1) manual page for details
transaction abort!
rollback completed
abort: invalid date: ' 1 4444' see hg(1) manual page for details
transaction abort!
rollback completed
abort: date exceeds 32 bits: 111111111111
transaction abort!
rollback completed
trouble committing bar!
abort: No such file or directory: .../test/bar