title: head() function failing
body: <p>I want to use the <code>head()</code> function to have an overview of the data set but it doesn't work.</p>
  <pre><code>&gt; library(haven)
  &gt; corona &lt;- read_sav(&quot;Corona_FB/Corona_FB/TRR265_CoronaFB_16-12-2020.sav&quot;)
  &gt; View(corona)
  &gt; head(corona)
  </code></pre>
  <blockquote>
  <p>Error in is.character(subclass) :
  argument &quot;subclass&quot; is missing, with no default</p>
  </blockquote>
  <pre><code>&gt; head(corona,n=3)
  </code></pre>
  <blockquote>
  <p>Error in is.character(subclass) :
  argument &quot;subclass&quot; is missing, with no default</p>
  </blockquote>