Closed Issue: Backspace and Delete exception when optionList is null [26686]

Release 30930, using IE7 on Win XP.

To reproduce:
1. ComboBox is databound with an empty collection (i.e. this._optionListItems is null and this._highlightedIndex is null)
2. Enter text into input
3. Backspace or Delete within input

Error:
"'this._optionListItems[...].text' is null or not an object"
from this line:
var _isExactMatch = this._isExactMatch(this._optionListItems[this._highlightedIndex].text, this.get_textBoxControl().value);
inside
_handleErasureKeys

Root cause:
Inside _ensureHighlightedIndex, call to _highlightListItem passes index of -1 (from firstMatch), thus __highlightedIndex remains null when accessed in _handleErasureKeys

Comments: This issue is fixed with release June 2012.