fix: correct no files check to compensate for pipes

nature/commands/greenhouse.lua

@@ -102,23 +102,23 @@ commander.register('greenhouse', function(args, sinks)
 		gh:addPage(page)
 	end
 
-	if #args ~= 0 then
 	for _, name in ipairs(args) do
 		local f <close> = io.open(name, 'r')
 		if not f then
 			sinks.err:writeln(string.format('could not open file %s', name))
 		end
-
 		local page = Page(name, f:read '*a')
 		gh:addPage(page)
 	end
-		ansikit.hideCursor()
-		gh:initUi()
-	else
+
+	if #gh.pages == 0 then
 		sinks.out:writeln [[greenhouse is the Hilbish pager library and command!
 usage: greenhouse <file>...
 
 example: greenhouse hello.md]]
+		return 1
 	end
 
+	ansikit.hideCursor()
+	gh:initUi()
 end)