loader: fix crash getting result from async load

panda/src/event/asyncFuture.I

@@ -103,6 +103,11 @@ set_result(TypedReferenceCount *result) {
   set_result(result, result);
 }
 
+INLINE void AsyncFuture::
+set_result(TypedWritableReferenceCount *result) {
+  set_result(result, result);
+}
+
 INLINE void AsyncFuture::
 set_result(const EventParameter &result) {
   set_result(result.get_ptr(), result.get_ptr());

panda/src/event/asyncFuture.h

@@ -86,6 +86,7 @@ PUBLISHED:
   INLINE void set_result(nullptr_t);
   INLINE void set_result(TypedObject *result);
   INLINE void set_result(TypedReferenceCount *result);
+  INLINE void set_result(TypedWritableReferenceCount *result);
   INLINE void set_result(const EventParameter &result);
 
 public: