Improved style nonce logic

Author: ankane

app/views/clockwork_web/home/index.html.erb

@@ -5,7 +5,7 @@
 
     <meta charset="utf-8" />
 
-    <%= content_tag :style, nonce: content_security_policy_nonce do %>
+    <%= content_tag :style, nonce: request.content_security_policy_nonce_directives&.include?("style-src") ? content_security_policy_nonce : nil do %>
       body {
         font-family: "Helvetica Neue", Arial, Helvetica, sans-serif;
         margin: 0;