CMS_decrypt_set1_*(): fix NULL deref on unsuitable content type

Fixes #19975
for CMS_decrypt_set1_pkey_and_peer() in the obvious way,
and a related potential crash in CMS_decrypt_set1_password().

The point is that the input might have an unexpected content type,
so a guard is needed at both places after `ec` is obtained.

Note that in CMS_decrypt_set1_pkey_and_peer() there was
no such ec != NULL guard for
```
    if (ris != NULL)
        debug = ec->debug;
```
maybe because it is implied here by ris != NULL.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
(Merged from #20209)

crypto/cms/cms_smime.c

@@ -708,11 +708,13 @@ int CMS_decrypt_set1_pkey_and_peer(CMS_ContentInfo *cms, EVP_PKEY *pk,
     CMS_EncryptedContentInfo *ec = ossl_cms_get0_env_enc_content(cms);
 
     /* Prevent mem leak on earlier CMS_decrypt_set1_{pkey_and_peer,password} */
-    OPENSSL_clear_free(ec->key, ec->keylen);
-    ec->key = NULL;
-    ec->keylen = 0;
+    if (ec != NULL) {
+        OPENSSL_clear_free(ec->key, ec->keylen);
+        ec->key = NULL;
+        ec->keylen = 0;
+    }
 
-    if (ris != NULL)
+    if (ris != NULL && ec != NULL)
         debug = ec->debug;
 
     cms_pkey_ri_type = ossl_cms_pkey_get_ri_type(pk);
@@ -826,9 +828,11 @@ int CMS_decrypt_set1_password(CMS_ContentInfo *cms,
     CMS_EncryptedContentInfo *ec = ossl_cms_get0_env_enc_content(cms);
 
     /* Prevent mem leak on earlier CMS_decrypt_set1_{pkey_and_peer,password} */
-    OPENSSL_clear_free(ec->key, ec->keylen);
-    ec->key = NULL;
-    ec->keylen = 0;
+    if (ec != NULL) {
+        OPENSSL_clear_free(ec->key, ec->keylen);
+        ec->key = NULL;
+        ec->keylen = 0;
+    }
 
     for (i = 0; i < sk_CMS_RecipientInfo_num(ris); i++) {
         ri = sk_CMS_RecipientInfo_value(ris, i);