From df04cb8a97da5c1de8a5cc14d6a0cfedb168e569 Mon Sep 17 00:00:00 2001
From: cgmossa <cgmossa@gmail.com>
Date: Tue, 28 Nov 2023 22:55:18 +0100
Subject: [PATCH] don't protect r `NULL`

---
 extendr-api/src/ownership.rs | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/extendr-api/src/ownership.rs b/extendr-api/src/ownership.rs
index 9115c161de..a70b529526 100644
--- a/extendr-api/src/ownership.rs
+++ b/extendr-api/src/ownership.rs
@@ -20,13 +20,17 @@ use libR_sys::{
 static OWNERSHIP: Lazy<Mutex<Ownership>> = Lazy::new(|| Mutex::new(Ownership::new()));
 
 pub(crate) unsafe fn protect(sexp: SEXP) {
-    let mut own = OWNERSHIP.lock().expect("protect failed");
-    own.protect(sexp);
+    if sexp != R_NilValue {
+        let mut own = OWNERSHIP.lock().expect("protect failed");
+        own.protect(sexp);
+    }
 }
 
 pub(crate) unsafe fn unprotect(sexp: SEXP) {
-    let mut own = OWNERSHIP.lock().expect("unprotect failed");
-    own.unprotect(sexp);
+    if sexp != R_NilValue {
+        let mut own = OWNERSHIP.lock().expect("unprotect failed");
+        own.unprotect(sexp);
+    }
 }
 
 pub const INITIAL_PRESERVATION_SIZE: usize = 100000;