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:
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):
Code:
  • 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
Code:
   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;