Added additional property check to guard against simulated touch events

[damassi]

This PR adds an additional check to check against the touches property in a native touch event, which may or may not exist if the user is creating or 'triggering' an artificial event. (The example being, when a dev wants to delegate mousedowns and mouseups to touchstart and touchend for sharing events across all platforms.)

[briangonzalez]

Looks good. How was this manifesting itself? Were you seeing errors?

[damassi]

Yup, it was throwing errors whenever I would attempt to drag anything on my desktop, which delegated touch events to mouse via jQuery. I suspect it was some kind of bubbling race condition (which comes first, the touch or the click?) which only manifests itself in certain contexts but this effectively fixed it.

[briangonzalez]

Sounds good, sir. Thanks for the PR!

[damassi]

np :)