[BUG] Method isc.StretchImg.inWhichPart() throws error when item is undefined.

[antanas.arvasevicius]

Hi, Isomorphic,

We've logged one strange error in browser and find out that sc.StretchImg.inWhichPart() don't check undefined conditions in:

inWhichPart : function () {
    if (this.vertical) {
        var num = this.inWhichPosition(this._imgSizes, this.getOffsetY());
    } else {
        var direction = (this.ignoreRTL || !this.isRTL()) ? isc.Canvas.LTR : isc.Canvas.RTL;
        var num = this.inWhichPosition(this._imgSizes, this.getOffsetX(), direction);
    }

    var item = this.items[num];
    // If the TabSet includes an "emptyButton" between the ScrollerForwardImg and the
    // ScrollerBackImg we need to take it into account, as the emptyButton is not a valid
    // target for inWhichPart(). So, if the cursor is in the emptyButton, we will return the
    // next item in the scroller, that will be the ScrollerBackImg.
    if (item.name == "emptyButton") item = this.items[num+1]; // <- HERE  if item is undefined then exception is thrown during property access "name" on undefined.
    return (item ? item.name : null); // <- HERE seems checking is done after property access should be done before.
}

Tested on SmartClient 10.1p 2019-02-13 (version) older also affected.

[Isomorphic]

This is an undocumented API and it's not clear that there's a valid usage in which a null check would be required, however, we've gone ahead and added such a check just in case.

Regards
Isomorphic Software

[antanas.arvasevicius]

Thanks!
But, we are not using this API directly, we've got exception from Scroolbar.handleMouseMove() in when mouse overs somehow unintentionally, unfortunately hasn't reporoduced this in dev env.