The print footprint feature fails when zooming with IE7&8

[asaunier]

When the print form is active (footprint is shown on the map), if the user zooms in / zooms out, the footprint handles and its border are incorrectly placed with IE7 and IE8. OK with IE9 or other browsers. See screenshot:

The problem occurs only with GGXP master (OK with projects running branch 1.3).

The error seems to be that shiftKey is undefined at

var reshape = !preserveAspectRatio && !(evt && evt.shiftKey);

https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Control/TransformFeature.js#L399