prev.location should always exist

[timwis]

Same logic as #227

[yoshuawuyts]

In 4.x prev will be null if it doesn't exist in a prior run - it turned out that having prev.location created way more complicated checks; e.g.

// this is the case in v4 now:
if (prev) // do thing with prev.location.search

// instead if prev.location always exists:
if (prev && prev.location && prev.location.search) // do thing with prev.location.search

In v4 I feel we're closer to being honest by allowing prev to null on a first render and then always have a destructured prev.location setup.

Does this make sense?

[yoshuawuyts]

_

[timwis]

Hm, @yoshuawuyts your requested change isn't showing up for me - it just says _