“book_offers” with same currency for taker_gets and taker_pays do not return "badMarket"

Expected response: `badMarket`
Actual response: `invalidParams`

Sample request:
`{
   "method": "book_offers",
   "params": [
       {
           "taker": "r97U4iT9m8Q2FeYnAQ1gFKGFDoKe8E7Rh",
           "taker_gets": {
               "currency": "XRP"
           },
           "taker_pays": {
               "currency": "XRP"
           },
           "limit":20
       }
   ]
}`