Fix a race condition between _queueCallback and dispose.

[michaelglas]

if _queueCallback is called just before dispose the transition complete callback will be called on the disposed component and almost certainly error out.

This can happen if a tooltip is removed just as it gets hidden.

[GeoSot]

@michaelglas Thank you for your contribution. Please support it adding some tests. (Preferable on baseComponent )

[michaelglas]

Done

[charlesfries]

@GeoSot Are we willing to merge this if conflicts are resolved?

[GeoSot]

@GeoSot Are we willing to merge this if conflicts are resolved?

@XhmikosR @julien-deramond any opinions on this?

It is not the best, but it is a fine defensive approach to solve clumsy implementations

[CatchABus]

This issue gives so much headache. We should be able to use dispose without having to worry about tooltips or modals being in show/hide transition.