Touchmove cancels valid current touches

[ehmorris]

Reproduce:

• Press a finger in the center
• Then press another and move it to the left
• The center touch is cancelled

This is a touchmove regression, probably due to the touches array changes made here: https://github.com/ehmorris/lunar-lander/commit/5092acbce9dff0a5825021a522b7ef011e2d200c

[ehmorris]

https://github.com/ehmorris/lunar-lander/commit/d205ac8c93eb19aae33307590c8e749290a2330c

[ehmorris]

^ This did not fix it. So it's unclear why some touches are being cancelled.