nvim: fix insert_modeline with empty commentstring, add (no)wrap

.config/nvim/lua/my/functions.lua

@@ -29,6 +29,9 @@ vim.api.nvim_create_autocmd({ 'BufWritePre' }, {
 -- Insert or update a modeline at the bottom of the buffer
 function M.insert_modeline()
     local comment_string = vim.o.commentstring
+    if comment_string == '' then
+        comment_string = '%s'
+    end
     local space_maybe = ''
     if string.match(comment_string, '%%s(.*)') ~= '' then
         space_maybe = ' '
@@ -47,6 +50,7 @@ function M.insert_modeline()
         ' tw=' .. vim.o.textwidth,
         ' ft=' .. vim.o.filetype,
         (vim.o.spell and ' spell' .. ' spl=' .. vim.o.spelllang or ''),
+        (vim.o.wrap and ' wrap' or ' nowrap'),
         ':',
         space_maybe
     }