Fix x509_get1_aia_by_method fallback case

Author: julek-wolfssl

src/x509.c

@@ -15179,13 +15179,20 @@ static WOLFSSL_STACK* x509_get1_aia_by_method(WOLFSSL_X509* x, word32 method,
             }
         }
     }
-    if (fallback != NULL && fallbackSz > 0) {
+    /* Only use fallback when nothing was found in the list */
+    if (wolfSSL_sk_num(ret) == 0 && fallback != NULL && fallbackSz > 0) {
         if (x509_aia_append_string(ret, fallback, (word32)fallbackSz) != 0) {
             wolfSSL_X509_email_free(ret);
             return NULL;
         }
     }
 
+    /* Return NULL when empty */
+    if (wolfSSL_sk_num(ret) == 0) {
+        wolfSSL_X509_email_free(ret);
+        ret = NULL;
+    }
+
     return ret;
 }