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
% file replaced with directory
adding a
% should fail - would corrupt dirstate
abort: file named 'a' already in dirstate
% directory replaced with file
adding a/a
% should fail - would corrupt dirstate
abort: directory named 'a' already in dirstate
% directory replaced with file
adding b/c/d
% should fail - would corrupt dirstate
abort: directory named 'b' already in dirstate