title: Xcode 7, Obj-C, "Null passed to a callee that requires a non-null argument"
body: <p>In Xcode 7, I'm getting this warning:</p>
  
  <pre><code>Null passed to a callee that requires a non-null argument
  </code></pre>
  
  <p>.. from this nil initialization of a NSMutableArray...</p>
  
  <pre><code>    sectionTitles = [[NSMutableArray alloc] initWithObjects:nil];
  </code></pre>
  
  <p>I've found that I should be using <code>removeAllObjects</code> instead.</p>
  
  <pre><code>    [sectionTitles removeAllObjects];
  </code></pre>
  
  <p>However, this doesn't allow me to evaluate a <code>sectionTitles.count == 0</code>. I did try <code>sectionTitles == nil</code>, however unless I use <code>iniWithObjects</code> I can't add objects later on.</p>
  
  <p>I need to set the array to nil or zero, when I refresh my datasource, when there's no records. I don't seem to be able to use <code>addObject</code> to add items unless I've used <code>initWithObjects</code>.</p>