test: check portable error message on issue46234.go

issue46234.go expects an error output "segmentation violation",
which is UNIX-specific. Check for "nil pointer dereference"
instead, which is emitted by the Go runtime and should work on all
platforms.

Should fix Windows builders.

Change-Id: I3f5a66a687d43cae5eaf6a9e942b877e5a248900
Reviewed-on: https://go-review.googlesource.com/c/go/+/321072
Trust: Cherry Mui <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>

Author: cherrymui

test/fixedbugs/issue46234.go

@@ -96,7 +96,7 @@ func main() {
 		log.Fatalf("Passed, expected an error")
 	}
 
-	want := []byte("segmentation violation")
+	want := []byte("nil pointer dereference")
 	if !bytes.Contains(output, want) {
 		log.Fatalf("Unmatched error message %q:\nin\n%s\nError: %v", want, output, err)
 	}