fix: crash in tags on enter for no results and random crash in previewer

lua/telescope/builtin/files.lua

@@ -458,6 +458,9 @@ files.tags = function(opts)
       action_set.select:enhance {
         post = function()
           local selection = action_state.get_selected_entry()
+          if not selection then
+            return
+          end
 
           if selection.scode then
             -- un-escape / then escape required

lua/telescope/previewers/buffer_previewer.lua

@@ -386,6 +386,10 @@ previewers.new_buffer_previewer = function(opts)
     opts.define_preview(self, entry, status)
 
     vim.schedule(function()
+      if not self or not self.state or not self.state.bufnr then
+        return
+      end
+
       if vim.api.nvim_buf_is_valid(self.state.bufnr) then
         vim.api.nvim_buf_call(self.state.bufnr, function()
           vim.cmd "do User TelescopePreviewerLoaded"