Per #2805, enhance the R differencing logic to handle NA strings in t…

…he header columns. Previously, differences that include the NA string were ignored. This enhances the compareStatLty() function to handle NA strings properly.

internal/test_unit/R_test/test_util.R

@@ -383,7 +383,9 @@ compareStatLty = function(stat1, stat2, lty, verb=0, strict=0){
 	# compare the information in the header columns
 	for(intCol in 2:21){
 		listMatch = apply(data.frame(dfV1[,intCol], dfV2[,intCol]), 1,
-				function(a){ a[1] == a[2] });
+	  			  function(a){ same = (a[1] == a[2]) | (is.na(a[1]) & is.na(a[2]));
+				               same[is.na(same)] = FALSE;
+				               return(same); });
 		intNumDiff = sum( !listMatch[ !is.na(listMatch) ] );
 		if( 0 < intNumDiff ){
 			if( 1 <= verb ){