It might happen that I don't have a dictionary for particular culture.
So I want that the 'Spell Checking' was unaccessible at such circumstances.

Is there any possibility to disable this functionality according to dictionaries available.

Please check Editor.DisableItemList Property - The toolbar items needed to be disabled going to this string. Example DisableItemList="Bold, New, Delete".

 

And in your code, you need to do something like:

 

Hope it helps.