It was possible to navigate to a CWD relative path if it was entered
in the directory and it happened to exist
(or entering relative paths: `./`, `../` etc).
After this, navigation in the file selector didn't work well, any paths
loaded would depend on the directory Blender was started in.
While CWD relative paths aren't prevented & can even be useful when
using paths passed in by scripts - there is no need for the file
selector to expose them to the user - potentially forwarding CWD
relative paths to operators where they can cause further problems.
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