Fix jumplist picker resume after bwipeout

With this change we will check if the provided buffer number is valid,
before querying its `buftype` option. This is necessary, because
currently we would fail with:
```
Error executing vim.schedule lua callback:
...scope.nvim/lua/telescope/previewers/buffer_previewer.lua:473:
Invalid buffer id: X
```
error, if we try to resume a jumplist picker after doing `:bwipeout`.

lua/telescope/previewers/buffer_previewer.lua

@@ -563,7 +563,10 @@ previewers.vimgrep = defaulter(function(opts)
 
     define_preview = function(self, entry)
       -- builtin.buffers: bypass path validation for terminal buffers that don't have appropriate path
-      local has_buftype = entry.bufnr and vim.api.nvim_buf_get_option(entry.bufnr, "buftype") ~= "" or false
+      local has_buftype = entry.bufnr
+          and vim.api.nvim_buf_is_valid(entry.bufnr)
+          and vim.api.nvim_buf_get_option(entry.bufnr, "buftype") ~= ""
+        or false
       local p
       if not has_buftype then
         p = from_entry.path(entry, true)