Fix signature of min/max proto getter

The getters for min and max proto version wrongly passed NULL instead of
0 as third argument to SSL_ctrl() and SSL_CTX_ctrl(). The third argument
is not used, but the error results in a compiler warning:

warning: passing argument 3 of ‘SSL_CTX_ctrl’ makes integer from pointer without a cast [-Wint-conversion]
int v = SSL_CTX_get_max_proto_version(self->ctx);

See https://github.com/openssl/openssl/pull/4364Signed-off-by: NChristian Heimes <christian@python.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NKurt Roeckx <kurt@roeckx.be>
Reviewed-by: NBen Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/5128)

include/openssl/ssl.h

@@ -1414,9 +1414,9 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 #define SSL_set_max_proto_version(s, version) \
         SSL_ctrl(s, SSL_CTRL_SET_MAX_PROTO_VERSION, version, NULL)
 #define SSL_get_min_proto_version(s) \
-        SSL_ctrl(s, SSL_CTRL_GET_MIN_PROTO_VERSION, NULL, NULL)
+        SSL_ctrl(s, SSL_CTRL_GET_MIN_PROTO_VERSION, 0, NULL)
 #define SSL_get_max_proto_version(s) \
-        SSL_ctrl(s, SSL_CTRL_GET_MAX_PROTO_VERSION, NULL, NULL)
+        SSL_ctrl(s, SSL_CTRL_GET_MAX_PROTO_VERSION, 0, NULL)
 
 #if OPENSSL_API_COMPAT < 0x10100000L
 /* Provide some compatibility macros for removed functionality. */