Add test that checks if custom callables don't crash when Err() is re…

…turned.

itest/rust/src/builtin_tests/containers/callable_test.rs

@@ -190,6 +190,14 @@ pub mod custom_callable {
         assert_eq!(sum3, 0.to_variant());
     }
 
+    #[itest]
+    fn callable_custom_with_err() {
+        let callable_with_err =
+            Callable::from_fn("on_error_doesnt_crash", |_args: &[&Variant]| Err(()));
+        // errors in godot but should not crash
+        assert_eq!(callable_with_err.callv(&varray![]), Variant::nil());
+    }
+
     #[itest]
     fn callable_from_fn_eq() {
         let a = Callable::from_fn("sum", sum);