pkcs12: fix ToPEM to not ignore non-nil error from getSafeContents

Fixes golang/go#19542

Change-Id: I60d2370d1d1e0763c72c9cc203ea2ff21123af73
Reviewed-on: https://go-review.googlesource.com/38261
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed