Add a test case for OSSL_HTTP_parse_url

Ensure we test the case where the port value is empty in the URL.

Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from openssl#22961)

test/http_test.c

@@ -347,7 +347,8 @@ static int test_http_url_invalid_prefix(void)
 
 static int test_http_url_invalid_port(void)
 {
-    return test_http_url_invalid("https://1.2.3.4:65536/pkix");
+    return test_http_url_invalid("https://1.2.3.4:65536/pkix")
+           && test_http_url_invalid("https://1.2.3.4:");
 }
 
 static int test_http_url_invalid_path(void)