Small follow-up fix for [6254] - `DefaultPermissionPolicy` needs to return `True` or `None` so that it doesn't break the chain. 
Small follow-up fix for [6254] - `DefaultPermissionPolicy` needs to return `True` or `None` so that it doesn't break the chain. 

Without the fix, the default `LegacyAttachmentPolicy` would never get called as defalt option is `permission_policies = DefaultPermissionPolicy, LegacyAttachmentPolicy`.

git-svn-id: eda3d06fcef731589ace1b284159cead3416df9b@6259 af82e41b-90c4-0310-8c96-b1721e28e2e2

walty8/trac,jun66j5/trac-ja,jun66j5/trac-ja,walty8/trac,netjunki/trac-Pygit2,walty8/trac,jun66j5/trac-ja,netjunki/trac-Pygit2,netjunki/trac-Pygit2,walty8/trac,jun66j5/trac-ja