Fix nightly coerce-container-to-any.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/debug.rs

@@ -100,7 +100,8 @@ pub fn trap() {
 
 #[must_use]
 pub fn panic_str(p: &Box<dyn Any + Send>) -> &'static str {
-	p.downcast_ref::<&str>()
+	(**p)
+		.downcast_ref::<&str>()
 		.copied()
 		.unwrap_or_default()
 }