fix lsp_code_action error when no code action available (#243)

the results variable can be nil when there's no code action available,

check for nil results before checking the length

lua/telescope/builtin.lua

@@ -229,7 +229,7 @@ builtin.lsp_code_actions = function(opts)
 
   local results = (results_lsp[1] or results_lsp[2]).result;
 
-  if #results == 0 then
+  if not results or #results == 0 then
     print("No code actions available")
     return
   end