[aabb-collider] data-aabb-collider-dynamic attribute not working without any value

[marlon360]

If you set the attribute data-aabb-collider-dynamic on the target, it is not recognized as dynamic.

Solution:
Write any value to the attribute.
<a-entity data-aabb-collider-dynamic="true">

Reason for that behavior:
el.dataset.aabbColliderDynamicequals '' which is equal to false.
Therefor this if-statement is false, when the attribute is added without any value.

// Dynamic, recalculate each tick.
      if (el.dataset.aabbColliderDynamic) {
        // Box.
        boundingBox.setFromObject(el.object3D);
        box = boundingBox;
        ...

Solution to support the attribute without any value:
Check against null:

// Dynamic, recalculate each tick.
      if (el.dataset.aabbColliderDynamic != null) {
        // Box.
        boundingBox.setFromObject(el.object3D);
        box = boundingBox;
        ...

[vincentfretin]

When the data-aabb-collider-dynamic is absent, el.dataset.aabbColliderDynamic is undefined, indeed el.dataset.aabbColliderDynamic != null is ok, but be careful el.dataset.aabbColliderDynamic !== null is not.
Better fix should probably be el.dataset.aabbColliderDynamic !== undefined

[vincentfretin]

and you need to replace the second condition if (!el.dataset.aabbColliderDynamic) by if (el.dataset.aabbColliderDynamic === undefined) otherwise box variable will be overridden anyway.

[vincentfretin]

I created #308 with the fix.