Invalid propagation in InputPlugin

[chancezeus]

There are 2 points of weirdness in the input plugin.

1. In the processDragEvents method on line 598 a return is used without a value, this results in undefined being returned which then causes total in the update method to become NaN and thus falsy => this will cause events to "fall through" to the parent scene since the update method thinks there are no elements with any active input in the current scene.
2. In the update method all process* methods return a total value except for processUpEvents => this will also cause events to "fall through" to the parent scene since pointerup will not be counted as being handled in the current scene