title: Error encountered with using rbindlist: column 25 of result is determined to be integer64 but maxType == 'Character' !=REALSXP
body: <p>I used the following function to merge all .csv files in my directory into one dataframe:</p>
  
  <pre><code>multmerge = function(mypath){
  filenames = list.files(path = mypath, full.names = TRUE)
  rbindlist(lapply(filenames,fread),fill = TRUE) }
  
  dataframe = multmerge(path)
  </code></pre>
  
  <p>This code produces this error: </p>
  
  <blockquote>
    <p>Error in rbindlist(lapply(filenames, fread), fill = TRUE) : Internal error: column 25 of result is determined to be integer64 but maxType=='character' != REALSXP</p>
  </blockquote>
  
  <p>The code has worked on the same csv files before...I'm not sure what's changed and what the error message means.</p>