Flag data for potential issues can result if fatal error if data is malformed

[JamesBisese]

Describe the bug

If a user uploads a dataset with malformed data the flagging procedure can raise an unhandled fatal error

To Reproduce

Steps to reproduce the behavior:

1. Go to 'Load'

2. Click on 'Upload data'

3. Load a dataset (exported from TADA as 'final)

4. Go to Flag data for potential issues and hit 'Run Tests' button

4. See error

Please include your Water Quality Portal data query inputs from the Load
data tab:

If applicable, include code to reproduce the behavior:

Error: (converted from warning) Error in dplyr::mutate: ℹ In argument: `MeasureQualifierCode.Split = strsplit(MeasureQualifierCode, ";")`.
Caused by error in `strsplit()`:
! non-character argument

Expected behavior

A clear and concise description of what you expected to happen.

Screenshots

If applicable, add screenshots to help explain your problem.

Additional context

Add any other context about the problem here.

Reminders for TADA contributors addressing this issue

Bug fixes should include the following work:

• Create or edit the code.

• Document all code using line/inline and/or multi-line/block comments
  to describe what is does.

• Create or edit tests in tests/testthat folder to help prevent and/or
  troubleshoot potential future issues.

• If your code edits impact other functionality in the shiny
  app, ensure those are updated as well.

• Run styler::style_pkg(), devtools::document(), and devtools::check()
  and address any new notes or issues before creating a pull request.

[JamesBisese]

Attached dataset is exported as Final Dataset and contains just the first 9 data rows
tada_output_ts241104085033.xlsx