title: Problems with UIStackView constraints
body: <p>I have a horizontal stack view, with an empty UIView on the left side and a label on the right side. In storyboard builder, it looks perfect (just look at the green row):</p>
  
  <p>However when I run the app on Sim or device, the color view just collapses and disappears:</p>
  
  <p>I have the stack view set to center alignment and proportional distribution.</p>
  
  <p>If I give the color view a set width, it works well in Sim/device, however I get a warning in the interface builder, which annoys me. I assume there's a more correct way, but I don't know what that is. With set width warning:</p>
  
  <p>It only allows me to delete the width=50 (the one I entered). It won't allow me to remove width=0 (not set by me, seems to be default).</p>
  
  <p>Anyone have any ideas?</p>