pkey: fix loading public keys with early OpenSSL 3.0.x releases

Treat an empty error queue after calling OSSL_DECODER_from_bio() as a
retryable error.

This is a follow-up to the previous commit 985ba27 (pkey: stop
retrying after non-retryable error from OSSL_DECODER). The commit broke
loading public keys on Ubuntu 22.04 LTS, which ships OpenSSL 3.0.2.

Author: rhenium

ext/openssl/ossl_pkey.c

@@ -103,7 +103,10 @@ ossl_pkey_read(BIO *bio, const char *input_type, int selection, VALUE pass,
     while (1) {
         if (OSSL_DECODER_from_bio(dctx, bio) == 1)
             break;
-        if (ERR_GET_REASON(ERR_peek_error()) != ERR_R_UNSUPPORTED)
+        // Error queue may not be populated in OpenSSL < 3.0.11 and < 3.1.3
+        // https://github.com/openssl/openssl/pull/21603
+        unsigned long err = ERR_peek_error();
+        if (err && ERR_GET_REASON(err) != ERR_R_UNSUPPORTED)
             break;
         if (BIO_eof(bio) == 1) {
             *retryable = 1;