Limit code duplication
When rescanning a non-existing bundle item path, rescan parent

For example when creating a new bundle (‘foo.tmBundle’) and then saving a new snippet in this bundle (‘bar.tmSnippet’) we may ask to rescan the ‘Snippets’ folder (in the bundle) before the bundle itself does a content (re)scan, which effectively makes the ‘Snippets’ rescan a no-op.

Should fix #1034
Don’t pass NULL_STR to path::entries
DFA nodes themselves should not dispose children

A DFA node may be disposed as part of DFA construction (because the node is redundant) and here it would have “next” pointers setup, which it should not follow in its destructor, since those nodes could still be used.

Fixes #1086