Increase code coverage

[DBartlettHP]

Achieving 100% code coverage on

-add.interval.col.R
-assertions.R

[DBartlettHP]

• adding a nocov to cover when clast is NA

• auciv.R contains a few new changes that I need to add a test for, however, my local machine does not contain these changes yet. [testing check = FALSE]
  

  pknca/R/auciv.R

  Lines 23 to 34 in b42d114

  	pk.calc.auciv <- function(conc, time, c0, auc, ..., options = list(), check=TRUE) {
  	if (check) {
  	assert_conc_time(conc = conc, time = time)
  	data <-
  	clean.conc.blq(
  	conc, time,
  	options = options,
  	check=FALSE
  	)
  	} else {
  	data <- data.frame(conc = conc, time = time)
  	}

[billdenney]

Can you please also fix these two issues (by changing na.omit() to stats::na.omit() on the indicated lines?

PKNCAdata.default: no visible global function definition for ‘na.omit’
  (/home/runner/work/pknca/pknca/check/PKNCA.Rcheck/00_pkg_src/PKNCA/R/class-PKNCAdata.R:186)
PKNCAdata.default: no visible global function definition for ‘na.omit’
  (/home/runner/work/pknca/pknca/check/PKNCA.Rcheck/00_pkg_src/PKNCA/R/class-PKNCAdata.R:193)