misc/wasm: ensure correct stack pointer in catch clauses

The stack pointer may have changed after a call from JavaScript into Go
code because of stack growth. The normal case already updated the
sp variable accordingly, but the catch case did not yet.

Fixes #45433

Change-Id: I3e0a33381929626f6b21902948935eb5ffb26c96
Reviewed-on: https://go-review.googlesource.com/c/go/+/321936


Trust: Richard Musiol <neelance@gmail.com>
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>