Fix a possible memleak in CMS_sign_receipt

When an error happens after cms_encode_Receipt
the ASN1_OCTET_STRING object "os" may be leaked.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22758)

crypto/cms/cms_smime.c

@@ -560,7 +560,7 @@ CMS_ContentInfo *CMS_sign_receipt(CMS_SignerInfo *si,
 {
     CMS_SignerInfo *rct_si;
     CMS_ContentInfo *cms = NULL;
-    ASN1_OCTET_STRING **pos, *os;
+    ASN1_OCTET_STRING **pos, *os = NULL;
     BIO *rct_cont = NULL;
     int r = 0;
     const CMS_CTX *ctx = si->cms_ctx;
@@ -622,6 +622,7 @@ CMS_ContentInfo *CMS_sign_receipt(CMS_SignerInfo *si,
     if (r)
         return cms;
     CMS_ContentInfo_free(cms);
+    ASN1_OCTET_STRING_free(os);
     return NULL;
 
 }