Ensure list has a value set before calling push (in FrameStateUtil).

This was causing a crash which breaks the browser window.
I believe this issue is related to the issues we have where wrong index is picked after closing / tearing off tab

Auditors: @NejcZdovc, @bbondy

js/state/frameStateUtil.js

@@ -393,7 +393,7 @@ function addFrame (state, frameOpts, newKey, partitionNumber, openInForeground,
  */
 function removeFrame (state, frameProps, framePropsIndex) {
   const frames = state.get('frames')
-  let closedFrames = state.get('closedFrames')
+  let closedFrames = state.get('closedFrames') || Immutable.List()
   const newFrames = frames.splice(framePropsIndex, 1)
 
   if (isValidClosedFrame(frameProps)) {