initialize state to empty object when getInitialState is not specified

[fdecampredon]

hareth: sometime I feel adding a mixin to all my component with getInitialState() { return {} }
vjeux: hareth: i'm surprised that it's not already the case
hareth: http://jsfiddle.net/F26zB/
vjeux: hareth: can you see if there's already a github issue opened for it/create one? I'm curious to see what other people have to say about this

It would avoid to force:

getInitialState: function () { return {} }

wen we need a state object, but do not need to initialize the content.

[sophiebits]

Your problem is that you're accessing uninitialized state properties?

[syranide]

For components that don't need state (which could easily be the majority), avoiding an allocation is a win. There has also been informal mentions of not allowing setState to set keys that doesn't already exist, i.e. they must be initially set to null or equivalent... for code sanity and improving performance/memory usage. I like that idea a lot.

[gaearon]

We won't make changes to createClass anymore.