[4.0.2a, 4.0.1] ToolTip error with config { anchor: 'bottom', anchorToTarget: false}

[xymovie]

When using ToolTip with anchor(arrow pointing) on mouse pointer (without target), it throws an exception.
The code works on ExtJs 3.x

anchor : String
If specified, indicates that the tip should be anchored to a particular side of the target element or mouse pointer ("top", "right", "bottom", or "left"), with an arrow pointing back at the target or mouse pointer. If constrainPosition is enabled, this will be used as a preferred value only and may be flipped as needed.

Test code:

   var tip = Ext.create('Ext.tip.ToolTip', {
        html: 'Test ToolTip anchor....',
        autoHide: false,
        anchor: 'bottom',
        anchorToTarget: false
    });
    tip.showAt(200, 100);

Error message on Chrome 12 (failed on Firefox 3.6.18 as well):

Uncaught TypeError: Cannot read property '0' of undefined
Ext.define.getTargetXYext-all-debug.js:37744
Ext.define.showext-all-debug.js:37973
Ext.define.showAtext-all-debug.js:26945
Base.callParentext-all-debug.js:2700
Ext.define.showAtext-all-debug.js:37579
Base.callParentext-all-debug.js:2700
Ext.define.showAtext-all-debug.js:37992
(anonymous function)test.js:192
isEventext-all-debug.js:10138
callext-all-debug.js:10094
 

   getTargetXY: function() {
        var me = this,
            mouseOffset;
        if (me.delegate) {
            me.anchorTarget = me.triggerElement;
        }
        if (me.anchor) {
            me.targetCounter++;
                var offsets = me.getOffsets(),
                    xy = (me.anchorToTarget && !me.trackMouse) ? me.el.getAlignToXY(me.anchorTarget, me.getAnchorAlign()) : me.targetXY,
                    dw = Ext.core.Element.getViewWidth() - 5,
                    dh = Ext.core.Element.getViewHeight() - 5,
                    de = document.documentElement,
                    bd = document.body,
                    scrollX = (de.scrollLeft || bd.scrollLeft || 0) + 5,
                    scrollY = (de.scrollTop || bd.scrollTop || 0) + 5,
                    axy = [xy[0] + offsets[0], xy[1] + offsets[1]], //xy is undefined
                    sz = me.getSize(),
                    constrainPosition = me.constrainPosition;