Fix NULL ptr dereference on EC_POINT *point

Use non-usual params of pkcs11 module will trigger a null ptr deref bug. Fix it for openssl#25493

Author: citypw

crypto/ec/ec_oct.c

@@ -74,6 +74,10 @@ size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *point,
                           point_conversion_form_t form, unsigned char *buf,
                           size_t len, BN_CTX *ctx)
 {
+    if ( point == NULL){
+        ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
+        return 0;
+    }
     if (group->meth->point2oct == 0
         && !(group->meth->flags & EC_FLAGS_DEFAULT_OCT)) {
         ERR_raise(ERR_LIB_EC, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);