Fix fetch of remote image with multiple Content-Type headers (#7749)

app/models/concerns/remotable.rb

@@ -24,11 +24,12 @@ module Remotable
           Request.new(:get, url).perform do |response|
             next if response.code != 200
 
-            content_type = parse_content_type(response.headers['content-type'])
+            content_type = parse_content_type(response.headers.get('content-type').last)
             extname      = detect_extname_from_content_type(content_type)
 
             if extname.nil?
-              matches  = response.headers['content-disposition']&.match(/filename="([^"]*)"/)
+              disposition = response.headers.get('content-disposition').last
+              matches     = disposition&.match(/filename="([^"]*)"/)
               filename    = matches.nil? ? parsed_url.path.split('/').last : matches[1]
               extname     = filename.nil? ? '' : File.extname(filename)
             end