🐛 Fixed logs showing an error when sending an email with no feature image

no issue

- we were attempting to read an image file to determine it's dimensions when no feature image was set. This wasn't a fatal error as it was handled gracefully and had no ill consequences but it was adding confusing errors to the logs

core/server/services/mega/post-email-serializer.js

@@ -155,6 +155,7 @@ const serialize = async (postModel, options = {isBrowserPreview: false, apiVersi
 
     // Outlook will render feature images at full-size breaking the layout.
     // Content images fix this by rendering max 600px images - do the same for feature image here
+    if (post.feature_image) {
         if (isUnsplashImage(post.feature_image)) {
             // Unsplash images have a minimum size so assuming 1200px is safe
             const unsplashUrl = new URL(post.feature_image);
@@ -181,6 +182,7 @@ const serialize = async (postModel, options = {isBrowserPreview: false, apiVersi
                 logging.error(err);
             }
         }
+    }
 
     const templateSettings = {
         showSiteHeader: settingsCache.get('newsletter_show_header'),