title: error with rvest html_table
body: <p>I am trying to scrape single table off of a list of 220 simple web sites. Each site has a single table on it that I want to scrape and put into a character vector, then rbind all 220 character vectors into a single data frame. </p>
  
  <p>Check if web pages exist, 200 = ok, 404 = page not found.</p>
  
  <pre><code>UrlListCheck &lt;- unlist ( lapply(lapply(url_list, html_session), function(x) {
      lapply(x$response$status_code, identity)
      } ))
  </code></pre>
  
  <p>all 220 pages are ok.</p>
  
  <p>check url format to download each html_table as character vector</p>
  
  <pre><code>215 -&gt; x ; html_table(html_session(url_list[[x]]))[[1]][,2]
  
  [1] ""                 "field2"         ""                
  [4] "field4" ""                 "field6"    
  [7] "field7"
  </code></pre>
  
  <p>The above works fine for all of the urls I check manually. </p>
  
  <p>The html_session works fine with lapply over the url list.</p>
  
  <pre><code>test1 &lt;- lapply(url_list, html_session)
  </code></pre>
  
  <p>But the html_table function throws an error with lapply over the list.</p>
  
  <pre><code>test2 &lt;- lapply(test1, html_table)
  
  Error in matrix(NA_character_, nrow = n, ncol = p): 
  invalid 'ncol' value (too large or NA)
  </code></pre>
  
  <p>Any suggestions?</p>
  
  <p>Output from the code below is what I want ultimately, which has worked for me on numerous other web pages with the same format on the same server.</p>
  
  <pre><code>TablesList &lt;- lapply(url_list, function(x) {
                              html_table(html_session(x))[[1]][,2] } )
  </code></pre>
  
  <p>Error in matrix(NA_character_, nrow = n, ncol = p): 
      invalid 'ncol' value (too large or NA)*</p>
  
  <pre><code>ResultDF &lt;- as.data.frame(do.call(rbind, TablesList))
  </code></pre>