regression on -current with vala-0.50.4

on -current dconf-editor doesn't build anymore with vala-0.50.4, but is OK with vala-0.50.3:
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../editor/bookmarks-list.vala:149.83-149.99: error: Argument 4: Cannot pass unowned ref argument to owned reference parameter
_create_bookmark_rows (bookmarks_variant, view_mode, ref main_list_store, ref main_list_box, ref bookmarks_hashtable);
^^^^^^^^^^^^^^^^^
../editor/bookmarks.vala:41.16-41.64: warning: [GtkChild] fields must be declared as `unowned'
[GtkChild] private BookmarksController bookmarks_controller;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../editor/bookmarks.vala:87.64-87.79: error: Argument 3: Cannot pass unowned ref argument to owned reference parameter
update_switch_label (ViewType.SEARCH, ViewType.FOLDER, ref switch_label); // init text with "Bookmark this Location"
^^^^^^^^^^^^^^^^
Compilation failed: 31 error(s), 89 warning(s)
ninja: build stopped: subcommand failed.
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