Prevent (but not fix) ‘Cannot read property 'getIn' of undefined’ in …

…getUpdatedSelectionState

Summary:
`getBlockTree()` can sometimes return undefined, despite its Flow type saying it always returns a list (eg. `List<any>`). This change protects against this possibility, falling back to the dev-time console warning below.

We can address the root cause later.

Reviewed By: claudiopro

Differential Revision: D19799354

fbshipit-source-id: 39a04a5de80853e5be76020a906f08a6c213685d

src/component/selection/getUpdatedSelectionState.js

@@ -36,15 +36,25 @@ function getUpdatedSelectionState(
 
   const anchorPath = DraftOffsetKey.decode(anchorKey);
   const anchorBlockKey = anchorPath.blockKey;
-  const anchorLeaf = editorState
-    .getBlockTree(anchorBlockKey)
-    .getIn([anchorPath.decoratorKey, 'leaves', anchorPath.leafKey]);
+  const anchorLeafBlockTree = editorState.getBlockTree(anchorBlockKey);
+  const anchorLeaf =
+    anchorLeafBlockTree &&
+    anchorLeafBlockTree.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 focusLeafBlockTree = editorState.getBlockTree(focusBlockKey);
+  const focusLeaf =
+    focusLeafBlockTree &&
+    focusLeafBlockTree.getIn([
+      focusPath.decoratorKey,
+      'leaves',
+      focusPath.leafKey,
+    ]);
 
   if (!anchorLeaf || !focusLeaf) {
     // If we cannot make sense of the updated selection state, stick to the current one.