tumblr: fix failure to upload certain video posts.

Fix failure to upload Tumblr video posts that contained a video URL of this form:

* https://va.media.tumblr.com/tumblr_rjoh0hR8Xe1teimlz_720.mp4

app/logical/source/extractor/tumblr.rb

@@ -29,7 +29,8 @@ class Source::Extractor
       end
 
       assets += inline_images
-      assets.map { |url| find_largest(url) }
+      assets = assets.map { |url| find_largest(url) }
+      assets.compact
     end
 
     def page_url
@@ -92,9 +93,8 @@ class Source::Extractor
       if parsed_image.full_image_url.present?
         image_url_html(parsed_image.full_image_url)&.at("img[src*='/#{parsed_image.directory}/']")&.[](:src)
       elsif parsed_image.variants.present?
-        # Look for the biggest available version on media.tumblr.com. A bigger
-        # version may or may not exist.
-        parsed_image.variants.find { |variant| http_exists?(variant) }
+        # Look for the biggest available version on media.tumblr.com. A bigger version may or may not exist.
+        parsed_image.variants.find { |variant| http_exists?(variant) } || image_url
       else
         parsed_image.original_url
       end

app/logical/source/url/tumblr.rb

@@ -123,12 +123,19 @@ class Source::URL::Tumblr < Source::URL
     subdomain&.ends_with?(".media") || subdomain&.in?(%w[data media])
   end
 
+  def video_url?
+    # https://va.media.tumblr.com/tumblr_rjoh0hR8Xe1teimlz_720.mp4
+    image_url? && file_ext.in?(%w[mp4 webm])
+  end
+
   def variants
     return [] unless @sample_size.present? && @filename.present?
     directory = "#{@directory}/" if @directory.present?
 
-    sizes = %w[1280 640 540 500h 500 400 250 100]
-    sizes.map { |size| "https://media.tumblr.com/#{directory}#{@filename}_#{size}.#{file_ext}" }
+    media_host = video_url? ? "va.media.tumblr.com" : "media.tumblr.com"
+    sizes = %w[1280 720 640 540 500h 500 400 250 100]
+
+    sizes.map { |size| "https://#{media_host}/#{directory}#{@filename}_#{size}.#{file_ext}" }
   end
 
   def page_url

test/unit/sources/tumblr_test.rb

@@ -96,6 +96,14 @@ module Sources
       )
     end
 
+    context "A video post with a https://va.media.tumblr.com/tumblr_*_720.mp4 URL" do
+      strategy_should_work(
+        "https://cloudstation.tumblr.com/post/697975577362251776/direct-quote-from-kaiba-post-battle-city",
+        image_urls: ["https://va.media.tumblr.com/tumblr_rjoh0hR8Xe1teimlz_720.mp4"],
+        download_size: 1_073_148,
+      )
+    end
+
     context "The source for a 'http://*.tumblr.com/post/*' answer post with inline images" do
       strategy_should_work(
         "https://noizave.tumblr.com/post/171237880542/test-ask",