Fix videos on public pages not using custom thumbnails (#14273)

app/views/media/player.html.haml

@@ -3,7 +3,7 @@
   = javascript_pack_tag 'public', integrity: true, crossorigin: 'anonymous'
 
 - if @media_attachment.video?
-  = react_component :video, src: @media_attachment.file.url(:original), preview: @media_attachment.file.url(:small), blurhash: @media_attachment.blurhash, width: 670, height: 380, editable: true, detailed: true, inline: true, alt: @media_attachment.description do
+  = react_component :video, src: @media_attachment.file.url(:original), preview: @media_attachment.thumbnail.present? ? @media_attachment.thumbnail.url : @media_attachment.file.url(:small), blurhash: @media_attachment.blurhash, width: 670, height: 380, editable: true, detailed: true, inline: true, alt: @media_attachment.description do
     %video{ controls: 'controls' }
       %source{ src: @media_attachment.file.url(:original) }
 - elsif @media_attachment.gifv?

app/views/statuses/_detailed_status.html.haml

@@ -29,7 +29,7 @@
   - if !status.media_attachments.empty?
     - if status.media_attachments.first.video?
       - video = status.media_attachments.first
-      = react_component :video, src: video.file.url(:original), preview: video.file.url(:small), blurhash: video.blurhash, sensitive: status.sensitive?, width: 670, height: 380, detailed: true, inline: true, alt: video.description do
+      = react_component :video, src: video.file.url(:original), preview: video.thumbnail.present? ? video.thumbnail.url : video.file.url(:small), blurhash: video.blurhash, sensitive: status.sensitive?, width: 670, height: 380, detailed: true, inline: true, alt: video.description do
         = render partial: 'statuses/attachment_list', locals: { attachments: status.media_attachments }
     - elsif status.media_attachments.first.audio?
       - audio = status.media_attachments.first

app/views/statuses/_simple_status.html.haml

@@ -35,7 +35,7 @@
   - if !status.media_attachments.empty?
     - if status.media_attachments.first.video?
       - video = status.media_attachments.first
-      = react_component :video, src: video.file.url(:original), preview: video.file.url(:small), blurhash: video.blurhash, sensitive: status.sensitive?, width: 610, height: 343, inline: true, alt: video.description do
+      = react_component :video, src: video.file.url(:original), preview: video.thumbnail.present? ? video.thumbnail.url : video.file.url(:small), blurhash: video.blurhash, sensitive: status.sensitive?, width: 610, height: 343, inline: true, alt: video.description do
         = render partial: 'statuses/attachment_list', locals: { attachments: status.media_attachments }
     - elsif status.media_attachments.first.audio?
       - audio = status.media_attachments.first