title: rtweet giving error in rbind when collecting large numbers of tweets
body: <p>I'm using the rtweet package in R to pull tweets for data analysis.
  When I run the following line of code requesting 18,000 tweets, everything works fine:</p>
  
  <pre><code>t &lt;- search_tweets("at", n=18000, lang='en', geocode='-25.609139,134.361949,3500km', since='2017-08-01', type='recent', retryonratelimit=FALSE)
  </code></pre>
  
  <p>But when I try to extend this to 100,000 tweets I get an error message</p>
  
  <pre><code>t &lt;- search_tweets("at", n=100000, lang='en', geocode='-25.609139,134.361949,3500km', since='2017-08-01', type='recent', retryonratelimit=TRUE)
  
  Finished collecting tweets!
  Error in rbind(deparse.level, ...) : 
    invalid list argument: all variables should have the same length
  </code></pre>
  
  <p>Why is this occurring and how do I solve this? Thanks</p>