* added null guard to fix null ref when pressing keyDown inside combobox
Improved an error message when view cannot be found
* Added a unit test to ensure combobox can process all key events
Found and fixed a new nullref
* Found a new bug when source is already present and combobox is added to a top view
* searchSet is auto initialized to new List() now to make the code a little bit safer
f602d3bd1d