FIX: Safely skip secure_media steps when it's not enabled (#11110)

* FIX: Safely skip secure_media steps when it's not enabled

* DEV: Secure media tests should enable secure media

lib/email/styles.rb

@@ -278,7 +278,7 @@ module Email
     def to_html
       # needs to be before class + id strip because we need to style redacted
       # media and also not double-redact already redacted from lower levels
-      replace_secure_media_urls
+      replace_secure_media_urls if SiteSetting.secure_media?
       strip_classes_and_ids
       replace_relative_urls
 

lib/pretty_text.rb

@@ -432,7 +432,7 @@ module PrettyText
 
     # images by themselves or inside a onebox
     doc.css('img[src]').each do |img|
-      url = if img.parent.classes.include?("aspect-image")
+      url = if img.parent.classes.include?("aspect-image") && img.attributes["srcset"].present?
 
         # we are using the first image from the srcset here so we get the
         # optimized image instead of the original, because an optimized