fix: custom extensions opts for commands (#404)

lua/telescope/command.lua

@@ -41,12 +41,10 @@ local function convert_user_opts(user_opts)
   setmetatable(_switch,_switch_metatable)
 
   for key,val in pairs(user_opts) do
-    if default_opts[key]  == nil then
-      print('[Telescope] argument not exists in default options')
-      return
-    end
+    if default_opts[key]  ~= nil then
       _switch[type(default_opts[key])](key,val)
     end
+  end
 end
 
 -- receive the viml command args