CL 131735 only updated nilptr3.go for the adjusted nil check. Adjust
nilptr3_wasm.go as well.

Change-Id: I4a6257d32bb212666fe768dac53901ea0b051138
Reviewed-on: https://go-review.googlesource.com/133495
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>