bhit_map fails when plates contain missing data

[Swarchal]

Error in if (platemap[row, "values"] > threshold) { : 
  missing value where TRUE/FALSE needed

platetools/R/bhit_map.R

Lines 102 to 111 in 2934bd8

	# calculate whether values are beyond the threshold; defined as hit or null
	for (row in 1:nrow(platemap)) {
	if (platemap[row, 'values'] > threshold) {
	platemap$hit[row] <- "hit"
	} else if (platemap[row, 'values'] < (-1*threshold)) {
	platemap$hit[row] <- "neg_hit"
	} else {
	platemap$hit[row] <- "null"
	}
	}

This can be fixed with an initial if statement, checking if the value is NaN, and if so, return an NaN.