title: "embedded nul in string" error with SparkR::collect
body: <p>I'm pulling in data from a api and keep getting the following error.</p>
  
  <p>I put together the sql query and am connecting to the instance for pulling the data. However, when I run collect, it given me an error.</p>
  
  <pre><code>soql_query = paste("SELECT Id, subject FROM Table")
  
  myDF2 &lt;- read.df(sqlContext, source="...", username=sf_username, password=sf_password, version=apiVersion, soql=soql_query)
  
  temp2 &lt;- SparkR::collect(myDF2)
  
  Error in rawToChar(string) : 
    embedded nul in string: 'VOID: \xe5,nq\b\x92ƹ\xc8Y\x8b\n\nAdd a new comment by Asako:\0\xb3\xe1\xf3Ȓ\xfd\xa0\bE\xe4\t06/29 09:23'
  In addition: Warning message:
  closing unused connection 6 (col) 
  </code></pre>
  
  <p>I've gone through and identified what column it is. It contains a lot of string data and sentences, so the error partially makes sense.</p>
  
  <p>I was wondering if there was any way to get around this issue.</p>