create check to highlight character NAs that should be empty cells

[rubenpp7]

This chunk bypasses the issue of character NAs in the text, but it doesn't highlight them to be fixed!!

EMODnetBiocheck/R/smallfunctions.R

Line 93 in 12163ec

# turn character NAs and spaces into an actual empty cell

We need to create a check that highlights it to the user before bypassing it

[rubenpp7]

@cyrilrader Maybe add an warning message to the cleandataframe() function when it uses the bypass chunk. That warning can then be integrated into the checkdataset() function so it's highlighted to the users.

Do not just create a check function in checkdataset() because the bypass happens at the very beginning of checkdataset() in the same step where data tables are read into R