Fix error when attempting to convert image w/o Content-Type header to data URI

lib/frenzy/pipeline/scrape_stage.ex

@@ -144,12 +144,12 @@ defmodule Frenzy.Pipeline.ScrapeStage do
 
     case Network.http_get(absolute_url) do
       {:ok, %Mojito.Response{body: body, headers: headers}} ->
-        {"Content-Type", content_type} =
         Enum.find(headers, fn {header, _value} -> header == "Content-Type" end)
-
-        if content_type in @content_type_allowlist do
+        |> case do
+          {"Content-Type", content_type} when content_type in @content_type_allowlist ->
             "data:#{content_type};base64,#{Base.encode64(body)}"
-        else
+
+          _ ->
             src
         end