Make connector cache more robust

[skippyall]

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Description

This should fix some issues with the external cache being null (see this discord mesage)

[skippyall]

To give some more detail, the previous code was likely to throw NPEs if the BlockCapabilityCache was not created in the first tick. It also included relics from old LazyOptional caching, which are now handled by BlockCapabilityCache, like chunk loading, block replacement and capability invalidation in general

[mrh0]

Thanks!