cmd/compile: check deferred nil interface call before wrapping it

Currently, for "defer i.M()" if i is nil it panics at the point of
defer statement, not when deferred function is called. We need to
do the nil check before wrapping it.

Updates #40724.

Change-Id: I62c669264668991f71999e2cf4610a9066247f9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/305549


Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>