fix highlight for file node

[pirey]

Description of Changes

Fix for #960 #953

The issue arise because NERDTreeFile is linked to Normal highlight. This caused the file node background to be the same as whatever color Normal is using, thus the highlight is different than the cursorline.

My solution is to clear bg highlight for NERDTreeFile.

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New Version Info

Author's Instructions

• Derive a new MAJOR.MINOR.PATCH version number. Increment the:
  • MAJOR version when you make incompatible API changes
  • MINOR version when you add functionality in a backwards-compatible manner
  • PATCH version when you make backwards-compatible bug fixes
• Update CHANGELOG.md, following the established pattern.

Collaborator's Instructions

• Review CHANGELOG.md, suggesting a different version number if necessary.
• After merging, tag the commit using these (Mac-compatible) bash commands:

  git checkout master
  git pull
  sed -n "$(grep -n -m2 '####' CHANGELOG.md | cut -f1 -d: | sed 'N;s/\n/,/')p" CHANGELOG.md | sed '$d'
  git tag -a $(read -p "Tag Name: " tag;echo $tag) -m"$(git show --quiet --pretty=%s)";git push origin --tags

[PhilRunninger]

Looks good. It looks like this bug dependent upon which editor and color scheme you're using. I use gruvbox, and never could reproduce the issue. I had to use solarized in nvim to see your change take effect.

Thanks for figuring it out.