The intermTypedNode pointer null check should be done before the pointer
is used, not after. In practice the pointer should never be null if
IntermUnary::promote() is consistent with the built-in function table,
but it's useful to have the null check as a fail-safe when developing.

Change-Id: I24e0d7399ef9d628f474e99fbca08dbd67fdd8c3
Reviewed-on: https://chromium-review.googlesource.com/240411Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>