what's a grammatical error in the sentence of this image??
http://i.imgur.com/JrUK0eo.jpg

Is there a grammatical error in the sentence in the red box?? because the guy in the image said so in his comment but I don't see any error there?

Question

what's a grammatical error in the sentence of this image??
http://i.imgur.com/JrUK0eo.jpg

Is there a grammatical error in the sentence in the red box?? because the guy in the image said so in his comment but I don't see any error there?

Answer

"If you don't one" doesn't make any sense. There seems to be a verb missing. It could be "if you don't want one,"  but since it seems to refer to advice, which is uncountable, it should be "if you don't want any."