We should probably avoid setting nonsensical state events

[turt2live]

Particularly for critical events like the power levels: if we don't have the power levels, or the user who is about to change them might unknowingly lose power, we should prevent that request from going through. An example is a homeserver sending a partial/no power level event and the user modifying some permission within that - because we copy the event from cache, riot will take the empty object, change the permission, then send over the new object. This leads to the user losing power unknowingly.

[turt2live]

Duplicate of #13900

Github bot be slow