title: Pandas giving IndexError on one dataframe but not on another similar dataframe
body: <p>I'm getting the error:</p>
  
  <pre><code>IndexError: index 0 is out of bounds for axis 0 with size 0
  </code></pre>
  
  <p>When trying to do:</p>
  
  <pre><code>df.loc[df["DATE"] == "xxx"].index[0]
  </code></pre>
  
  <p>On this csv-file:</p>
  
  <pre><code>DATE,x,y
  123,5,7
  </code></pre>
  
  <p>But it works perfectly fine on this csv-file:</p>
  
  <pre><code>Date,X,Y
  1991-07-09,123,123
  </code></pre>
  
  <p>Why?</p>
  
  <p>xxx is changed out to 123 and 1991-07-09 respectively.</p>