refactored missing link scenario to make more sense

+ 404 code, stay on the current page, and load the form
+ also simplified the logic for the create action if the link doesn't
  already exist

app.rb

@@ -19,11 +19,10 @@ class App < Roda
 
     r.get String do | url_code |
       link = links.filter(:code => url_code)
-      if link.first.nil?
-        flash['message'] = "Link #{url_code} doesn't exist"
-        r.redirect '/'
-      end
-      r.redirect link.first[:url]
+      r.redirect link.first[:url] unless link.first.nil?
+      @message = "Link #{url_code} doesn't exist"
+      response.status = 404
+      view :home
     end
 
     r.post "create" do
@@ -32,7 +31,7 @@ class App < Roda
         flash['message'] = "Please enter a valid URL";
         r.redirect '/'
       end
-      if nil == links.filter(:url => url).first
+      if links.filter(:url => url).first.nil?
         code = SecureRandom.urlsafe_base64 4
         links.insert(url: url, code: code) 
         @message = "Link created"