Fix race condition in ResponderTouchHistoryStore

[marcshilling]

On a cold boot of my React Native app, if the first touch on the screen is a scroll on a ListView/ScrollView, there appears to be a race condition and recordMoveTouchData is called before recordStartTouchData, therefore touchHistory.touchBank is not properly initialized.

Upon the first call,
var touchTrack = touchBank[touch.identifier];
touchTrack is undefined here, causing the crash. This code change resolves the problem by properly initializing the touchBank. Not sure if this is the correct approach, because it's probably an indication of a deeper problem, but wanted to start a conversation about it.

[jimfb]

It seems to me that this is not the correct fix. React-native shouldn't be sending a move event before a start event, right?

[marcshilling]

That's the exactly what I was thinking, but...I don't know.

[jimfb]

I'm going to close this out, because I don't think this is the right fix. It would just hide the problem, making it more difficult to debug/reproduce/witness. Also, with this fix, you would still be loosing events, which is a bad user experience. I'm going to close this out in favor of tracking facebook/react-native#5246. If the RN team bounces it back here, we can re-investigate.