title: Null passed to a callee that requires a non-null argument with UIImageView
body: <p>After upgrading to Xcode7.2, I have this warning:</p>
  
  <pre><code>Null passed to a callee that requires a non-null argument
  </code></pre>
  
  <p>I only know how to satisfy non-null requirement to avoid this warning for string by using @"" instead of nil. <strong>However I don't know how to do so in the case of UIImageView</strong> and here below is my code:</p>
  
  <pre><code>if (imageFile)
          {
              UIImageView *imageLabel = [[UIImageView alloc] init];
              [imageLabel setTag:CellImageLabelTag];
              [cell.contentView addSubview:imageLabel];
  
          } else {
              UIImageView *imageLabel = [[UIImageView alloc] init];
              [imageLabel setTag:CellImageLabelTag];
              [cell.contentView addSubview:nil]; //warning here
          }
  </code></pre>
  
  <p>Please give me some advice. Thanks in advance.</p>