Union Relationship Ref to Wildcard (Edge Case)

[Epsola]

Describe the bug
Creating this as a bug so that it doesn't get forgotten. There is an issue with queries and union relationship enums. See chat for details...

To Reproduce
See discord discussion

[SanderMertens]

Bit more context (before the discord thread expires):

It looks like there is an issue with queries for union relationships, where the union relationship is resolved as a reference (from another entity, like a prefab or parent).

The issue shows up as a query attempting to resolve a wildcard id on a reference, which fails.

[KenthJohan]

A related issue when a query term uses parent union:

ECS_ENTITY(world, Movement, EcsUnion);
ECS_TAG(world, Walking);
ECS_TAG(world, Running);
ecs_query_t *q = ecs_query_init(world, &(ecs_query_desc_t){
.filter.terms = {{.id = ecs_pair(Movement, Running), .src.trav = EcsChildOf, .src.flags = EcsUp}}
});
ecs_entity_t e0 = ecs_new_entity(world, "e0");
ecs_add_pair(world, e0, Movement, Running);
ecs_entity_t e1 = ecs_new_entity(world, "e1");
ecs_add_pair(world, e1, EcsChildOf, e0);

Gives: fatal: flecs.c: 8122: assert: ecs_id_is_valid(world, id) INVALID_PARAMETER