Fix scraper error with invalid hostname

lib/philomena_proxy/scrapers.ex

@@ -56,16 +56,17 @@ defmodule PhilomenaProxy.Scrapers do
   def scrape!(url) do
     uri = URI.parse(url)
 
-    @scrapers
-    |> Enum.find(& &1.can_handle?(uri, url))
-    |> wrap()
-    |> Enum.map(& &1.scrape(uri, url))
-    |> unwrap()
-  end
+    cond do
+      is_nil(uri.host) ->
+        # Scraping without a hostname doesn't make sense because the proxy cannot fetch it, and
+        # some scrapers may test properties of the hostname.
+        nil
 
-  defp wrap(nil), do: []
-  defp wrap(res), do: [res]
-
-  defp unwrap([result]), do: result
-  defp unwrap(_result), do: nil
+      true ->
+        # Find the first scraper which can handle the URL and process, or return nil
+        Enum.find_value(@scrapers, nil, fn scraper ->
+          scraper.can_handle?(uri, url) && scraper.scrape(uri, url)
+        end)
+    end
+  end
 end