Check table existence on prepare_for_foreign_keys (#4225)

* Check table existence on prepare_for_foreign_keys

* Remove trailing whitespace

lib/tasks/mastodon.rake

@@ -232,9 +232,16 @@ namespace :mastodon do
     task prepare_for_foreign_keys: :environment do
       # All the deletes:
       ActiveRecord::Base.connection.execute('DELETE FROM statuses USING statuses s LEFT JOIN accounts a ON a.id = s.account_id WHERE statuses.id = s.id AND a.id IS NULL')
-      ActiveRecord::Base.connection.execute('DELETE FROM account_domain_blocks USING account_domain_blocks adb LEFT JOIN accounts a ON a.id = adb.account_id WHERE account_domain_blocks.id = adb.id AND a.id IS NULL')
-      ActiveRecord::Base.connection.execute('DELETE FROM conversation_mutes USING conversation_mutes cm LEFT JOIN accounts a ON a.id = cm.account_id WHERE conversation_mutes.id = cm.id AND a.id IS NULL')
-      ActiveRecord::Base.connection.execute('DELETE FROM conversation_mutes USING conversation_mutes cm LEFT JOIN conversations c ON c.id = cm.conversation_id WHERE conversation_mutes.id = cm.id AND c.id IS NULL')
+
+      if ActiveRecord::Base.connection.table_exists? :account_domain_blocks
+        ActiveRecord::Base.connection.execute('DELETE FROM account_domain_blocks USING account_domain_blocks adb LEFT JOIN accounts a ON a.id = adb.account_id WHERE account_domain_blocks.id = adb.id AND a.id IS NULL')
+      end
+
+      if ActiveRecord::Base.connection.table_exists? :conversation_mutes
+        ActiveRecord::Base.connection.execute('DELETE FROM conversation_mutes USING conversation_mutes cm LEFT JOIN accounts a ON a.id = cm.account_id WHERE conversation_mutes.id = cm.id AND a.id IS NULL')
+        ActiveRecord::Base.connection.execute('DELETE FROM conversation_mutes USING conversation_mutes cm LEFT JOIN conversations c ON c.id = cm.conversation_id WHERE conversation_mutes.id = cm.id AND c.id IS NULL')
+      end
+
       ActiveRecord::Base.connection.execute('DELETE FROM favourites USING favourites f LEFT JOIN accounts a ON a.id = f.account_id WHERE favourites.id = f.id AND a.id IS NULL')
       ActiveRecord::Base.connection.execute('DELETE FROM favourites USING favourites f LEFT JOIN statuses s ON s.id = f.status_id WHERE favourites.id = f.id AND s.id IS NULL')
       ActiveRecord::Base.connection.execute('DELETE FROM blocks USING blocks b LEFT JOIN accounts a ON a.id = b.account_id WHERE blocks.id = b.id AND a.id IS NULL')