title: Error n tweets were requested but the API can only return 0
body: <p>I am unable to retrieve any tweets using twitteR package in R. For example this request:</p>
  
  <pre><code>nbahash_tweets = searchTwitter("#nba",since='2013-01-01', until='2014-02-25',n=20)
  </code></pre>
  
  <p>Shows me this warning message:</p>
  
  <blockquote>
    <p>Warning message: In doRppAPICall("search/tweets", n, params = params,
    retryOnRateLimit = retryOnRateLimit,  :   20 tweets were requested but
    the API can only return 0</p>
  </blockquote>
  
  <p>What could be the reason of the problem?</p>