Check for empty frame when window state isn't updated yet

Fix #10749

I don't think I can add a test for this since it's so unfrequent but it will go away once we get rid of frame state

Author: bbondy

js/stores/windowStore.js

@@ -159,7 +159,7 @@ const newFrame = (state, frameOpts) => {
     const tabId = frameOpts.tabId
     const frame = frameStateUtil.getFrameByTabId(state, tabId)
     state = frameStateUtil.updateTabPageIndex(state, tabId)
-    if (active) {
+    if (active && frame) {
       // only set the activeFrameKey if the tab is already active
       state = state.set('activeFrameKey', frame.get('key'))
     } else {