Fixing IE8 bug where position returns undefined and eventually NaNpx. Only happens in conjunction w/ older jQuery (1.4.2 here).

Fixing IE8 bug where position.left was returning NaN. Stemming from the updateAfterSlideTransition() having a case where the position variable could be undefined. Other browsers ignore this but IE8 throws an error. Only happens when using an older version of jQuery. This fix is pertinent to those required to use older jQuery versions due to company policy.