>>>This is what I wanted to confirm. Therefore, I know now that I need to find where and how some empty string gets into the textbox.
>>>
>>
>>You don't need an empty string. Just double click somewhere in the textbox.
>
>Interesting you say this. I just double clicked in the field and what I see is a highlighted/selected part of the textbox. Does it mean that there is an empty string in this textbox?

No, it means that you can start typing at that point even if textbox value was a zero-length string before.