FIX: Remove post/topic image_url on post edits

- resets image_url when image is removed from first post on edit
- excludes onebox icons from being featured as topic/post images

lib/cooked_post_processor.rb

@@ -216,7 +216,9 @@ class CookedPostProcessor
     # minus emojis
     @doc.css("img.emoji") -
     # minus images inside quotes
-    @doc.css(".quote img")
+    @doc.css(".quote img") -
+    # minus onebox site icons
+    @doc.css("img.site-icon")
   end
 
   def oneboxed_images
@@ -488,7 +490,11 @@ class CookedPostProcessor
 
   def update_post_image
     img = extract_images_for_post.first
-    return if img.blank?
+    if img.blank?
+      @post.update_column(:image_url, nil) if @post.image_url
+      @post.topic.update_column(:image_url, nil) if @post.topic.image_url
+      return
+    end
 
     if img["src"].present?
       @post.update_column(:image_url, img["src"][0...255]) # post

spec/components/cooked_post_processor_spec.rb

@@ -774,6 +774,21 @@ describe CookedPostProcessor do
           post.topic.reload
           expect(post.topic.image_url).to be_present
         end
+
+        it "removes image if post is edited and no longer has an image" do
+          FastImage.stubs(:size)
+
+          cpp.post_process
+          post.topic.reload
+          expect(post.topic.image_url).to be_present
+          expect(post.image_url).to be_present
+
+          post.update!(raw: "This post no longer has an image.")
+          CookedPostProcessor.new(post).post_process
+          post.topic.reload
+          expect(post.topic.image_url).not_to be_present
+          expect(post.image_url).not_to be_present
+        end
       end
 
       context "post image" do