title: Xcode storyboard: Internal error. Please file a bug
body: <p>While editing in the storyboard, specifically assigning a view controller to a specific class, I suddenly encountered this error when I wanted to run the project.</p>
  
  <p>Main.storyboard: Internal error. Please file a bug at bugreport.apple.com and attach "/var/folders/79/_jh611t15qsfcx165_jv_20h0000gn/T/IB-agent-diagnostics_2015-10-28_00-33-12_730000".</p>
  
  <p>And now I can't run my project anymore. I couldn't find any information regarding to this anywhere else. Did anyone encounter this before?</p>
  
  <p><a href="https://i.stack.imgur.com/ACBQa.png"><img src="https://i.stack.imgur.com/ACBQa.png" alt="enter image description here"></a></p>