return after promises are rejected

[fantapop]

Exit after rejecting the promise so we don't continue to try and use navigator.accelerometer which is undefined.

[gortok]

This isn't a bad idea; but we need better logic here; there should be conditional logic if/else around so you're not using the plugin if it's undefined. A little more extensive work would need to be done against this PR to have to included.

[fantapop]

I'm not really following. By returning the rejected promise, the plugin will not be used.