physics.c: can_collide now checks for object_is_valid before comfirming other variables

src/corelib/object.h

@@ -25,7 +25,7 @@ object_t object_default();
 
 void object_draw_sprite(object_t* object);
 static inline
-int object_is_valid(object_t* object) {
+int object_is_valid(const object_t* object) {
 	return object == NULL || object->active == 0;
 }
 

src/corelib/physics.c

@@ -24,7 +24,7 @@ void object_broadcast_collision(object_t* this, object_t* other) {
 	}
 }
 short can_collide(const object_t* this) {
-	return this->active && this->enabled;
+	return object_is_valid(this) && this->enabled;
 }
 
 static inline