Make PreviewCard records reuseable between statuses (#4642)

* Make PreviewCard records reuseable between statuses

**Warning!** Migration truncates preview_cards tablec

* Allow a wider thumbnail for link preview, display it in horizontal layout (#4648)

* Delete preview cards files before truncating

* Rename old table instead of truncating it

* Add mastodon:maintenance:remove_deprecated_preview_cards

* Ignore deprecated_preview_cards in schema definition

* Fix null behaviour

app/models/media_attachment.rb

@@ -142,9 +142,11 @@ class MediaAttachment < ApplicationRecord
 
   def populate_meta
     meta = {}
+
     file.queued_for_write.each do |style, file|
       begin
         geo = Paperclip::Geometry.from_file file
+
         meta[style] = {
           width: geo.width.to_i,
           height: geo.height.to_i,
@@ -155,6 +157,7 @@ class MediaAttachment < ApplicationRecord
         meta[style] = {}
       end
     end
+
     meta
   end