Implemented changes required by #78

[numeredev]

SUMMARY

Implements necessary changes for #78

Reviewers: @numere-org/maintainers

IMPLEMENTATION

• Implementation: Resolved the typo and replaced the std::string::replace() with a plain for loop.
• Implementation test: Created a table with multiple head rows and saved that to XLS successfully.

DOCUMENTATION

• [x] ChangesLog updated
• [x] Code changes commented
• Documentation articles:
  • [ ] corresponding documentation articles updated
  • [ ] new documentation articles created
  • [x] not needed
• Language files:
  • [ ] corresponding language files updated
  • [x] not needed

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TESTS BY REVIEWERS

• [x] Added to the automatic SW tests
• [x] Tested manually

[raphael-sys]

Is a automated software test necessary here? I would need to export a file and then re-import it. Possible, not sure if it is worth the extra effort, as the problem is unlikely to occur again.

[numeredev]

This can be done with an automatic test and you could check the results after re-importing. Does not really check the single fix (more like two of them), but still can be used as a regression test.