Memory leak and uncleared ref for static components.

[TerenceZ]

In brief, when unbuild() the static component (e.g., caused by the v-if), it won't invoke the unsetCurrent() to clean the ref in its context, which leads to the situation that the component's destroyed or being destroyed (because the deferred cleanup) but its context can still manipulate it by its ref, which is unexpected. For example and more detail, check the demo.

[yyx990803]

Thanks for the detailed report, really appreciated!