Perform addn even if not skip_empty.

Property definitions

nitc $ PrettyPrinterVisitor :: forcen
	# Perform `addn` even if not `skip_empty`.
	fun forcen do
		if current_length == 0 and last_line_is_blank then return
		previous_length = current_length
		current_length = 0
		wait_addn += 1
	end
src/pretty.nit:254,2--260,4