Unable to use blocked and distance

When I create a pathfinder that uses both blocked and distance, the blocked always gets ignored.
Am I doing something wrong?

```
graph.addLink("shopA","liftA",{weight:10, wheelchair: true});
graph.addLink("liftA","liftB",{weight:1, wheelchair: true});
graph.addLink("liftB","shopB",{weight:10, wheelchair: true});
graph.addLink("shopA","stairsA",{weight:5, wheelchair: true});
graph.addLink("stairsA","stairsB",{weight:1, wheelchair: false});
graph.addLink("stairsB","shopB",{weight:5, wheelchair: true});

let pathFinder_wc = ngraphPath.aStar(graph, {
blocked(fromNode, toNode, link) {
return !link.data.wheelchair;
},
distance(fromNode, toNode, link) {
return link.data.weight;
},
});
```

let path = pathFinder_wc.find("shopA","shopB");

path always returns the shortest regardless of stairsA -> stairsB is wheelchair false

Start at the ngraphPath.aStar entry point and reproduce the issue with the graph and blocked/distance callbacks shown here. Trace why the wheelchair=false link is still considered; done means the returned path excludes that link while still using the supplied weights.

Written by the indexing model from the issue text.