add nocov for knitr_print

Author: ben-schwen

R/print.data.table.R

@@ -293,8 +293,8 @@ trunc_cols_message = function(not_printed, abbs, class, col.names){
 
 # Maybe add a method for repr::repr_text.  See https://github.com/Rdatatable/data.table/issues/933#issuecomment-220237965
 knit_print.data.table = function(x, ...) {
-  if (!shouldPrint(x)) return(invisible(x))
-  NextMethod()
+  if (!shouldPrint(x)) return(invisible(x)) # nocov
+  NextMethod() # nocov
 }
 record_print.data.table = function(x, ...) {
   if (!shouldPrint(x)) return(character()) # nocov