Updating selection between rendering can crash

There is a timing window that exists from when a new editorState is passed into draftjs as a prop until that new state is rendered. If an onSelect event fires in this time, then the code will throw because the editorState doesn't yet match the DOM state. getUpdatedSelectionState should detect this case and just return editorState.getSelection() in this scenario.

src/component/selection/getUpdatedSelectionState.js

@@ -39,15 +39,27 @@ function getUpdatedSelectionState(
 
   const anchorPath = DraftOffsetKey.decode(anchorKey);
   const anchorBlockKey = anchorPath.blockKey;
-  const anchorLeaf = editorState
-    .getBlockTree(anchorBlockKey)
-    .getIn([anchorPath.decoratorKey, 'leaves', anchorPath.leafKey]);
+  const anchorBlockTree = editorState.getBlockTree(anchorBlockKey);
+  if (!anchorBlockTree) {
+    return selection;
+  }
+  const anchorLeaf = anchorBlockTree.getIn([
+    anchorPath.decoratorKey,
+    'leaves',
+    anchorPath.leafKey,
+  ]);
 
   const focusPath = DraftOffsetKey.decode(focusKey);
   const focusBlockKey = focusPath.blockKey;
-  const focusLeaf = editorState
-    .getBlockTree(focusBlockKey)
-    .getIn([focusPath.decoratorKey, 'leaves', focusPath.leafKey]);
+  const focusBlockTree = editorState.getBlockTree(focusBlockKey);
+  if (!focusBlockTree) {
+    return selection;
+  }
+  const focusLeaf = focusBlockTree.getIn([
+    focusPath.decoratorKey,
+    'leaves',
+    focusPath.leafKey,
+  ]);
 
   const anchorLeafStart: number = anchorLeaf.get('start');
   const focusLeafStart: number = focusLeaf.get('start');