FunctionsEGL::terminatePtr could be null if initialization failed,
so check it before use to avoid crashing.

Change-Id: Ide9378c8e26749ab9d58c01cb36cd923836cde98
Reviewed-on: https://chromium-review.googlesource.com/506627Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>