Fix to minor bug concerning missing object

[vincentvanhees]

Making sure object defaultGuiderCorrected is present within function g.part4 under all scenarios

Fixes #1438

Checklist before merging:

• Existing tests still work (check by running the test suite, e.g. from RStudio).
• Added tests (if you added functionality) or fixed existing test (if you fixed a bug).
• Clean code has been attempted, e.g. intuitive object names and no code redundancy.
• Documentation updated:
  • Function documentation
  • Chapter vignettes for GitHub IO
  • Vignettes for CRAN
• Corresponding issue tagged in PR message. If no issue exist, please create an issue and tag it.
• Updated release notes in inst/NEWS.Rd with a user-readable summary. Please, include references to relevant issues or PR discussions.
• If you think you made a significant contribution, add your name to the contributors lists in the DESCRIPTION, zenodo.json, and inst/CITATION files.
• GGIR parameters were added/removed. If yes, please also complete checklist below.