Only unlock in rsa_get_blinding when locking was successful

CLA: trivial

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/28438)

crypto/rsa/rsa_ossl.c

@@ -264,9 +264,9 @@ static BN_BLINDING *rsa_get_blinding(RSA *rsa, BN_CTX *ctx)
                 BN_BLINDING_free(ret);
                 ret = NULL;
             }
-        }
             CRYPTO_THREAD_unlock(rsa->lock);
         }
+    }
 
     return ret;
 }