[roll] Roll fuchsia [elflib] Fix UB for invalid segment data

Pointer arithmetic on nullptrs is invalid and trips ubsan.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1163052
Original-Revision: b99fdbb694665f37cf1f667e371a1c6ad8b34b78
GitOrigin-RevId: c35b075352231598db8a45f957d3890c851e4419
Change-Id: I8ff0745729850b34a6b496b9ea8a3204051913f8
diff --git a/stem b/stem
index 786c5e7..f300e08 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="ac06a68ed5687824683100c96a0db9e9de99dd75"/>
+             revision="b99fdbb694665f37cf1f667e371a1c6ad8b34b78"/>
   </projects>
   <hooks>
     <hook name="install-environment"