fix: preview = true (#2168)

lua/telescope/previewers/buffer_previewer.lua

@@ -152,11 +152,13 @@ local scroll_fn = function(self, direction)
 end
 
 previewers.file_maker = function(filepath, bufnr, opts)
-  opts = opts or {}
-  opts.preview = opts.preview or {}
+  opts = vim.F.if_nil(opts, {})
+  -- TODO(conni2461): here shouldn't be any hardcoded magic numbers ...
+  opts.preview = vim.F.if_nil(opts.preview, {})
   opts.preview.timeout = vim.F.if_nil(opts.preview.timeout, 250) -- in ms
   opts.preview.filesize_limit = vim.F.if_nil(opts.preview.filesize_limit, 25) -- in mb
   opts.preview.msg_bg_fillchar = vim.F.if_nil(opts.preview.msg_bg_fillchar, "╱") -- in mb
+  opts.preview.treesitter = vim.F.if_nil(opts.preview.treesitter, true)
   if opts.use_ft_detect == nil then
     opts.use_ft_detect = true
   end