doc/go1.18: add docs on FieldByIndexErr

From:
https://go-review.googlesource.com/c/go/+/357962/

Updates #47694

Change-Id: I2d43dcbd28c03457b55eada26e87f7710a113b0c
Reviewed-on: https://go-review.googlesource.com/c/go/+/368364
Trust: Jeremy Faller <jeremy@golang.org>
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/doc/go1.18.html b/doc/go1.18.html
index 5692a06..8f0fc1f 100644
--- a/doc/go1.18.html
+++ b/doc/go1.18.html
@@ -459,7 +459,10 @@
     </p>
 
     <p><!-- CL 357962 -->
-      TODO: <a href="https://golang.org/cl/357962">https://golang.org/cl/357962</a>: add FieldByIndexErr
+      <a href="/pkg/reflect#Value.FieldByIndexErr"><code>Value.FieldByIndexErr</code></a>
+      has been added to avoid the panic that occurs in
+      <a href="/pkg/reflect#Value.FieldByIndex"><code>Value.FieldByIndex</code></a>
+      when stepping through a nil pointer to an embedded struct.
     </p>
   </dd>
 </dl><!-- reflect -->