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
adding dir/bar
adding foo
dir/bar
foo
adding dir/bar_2
adding foo_2
dir/bar_2
foo_2
adding a
adding c
adding b
adding d
removing a
removing c
recording removal of a as rename to b (100% similar)