Preference - pop-up or high-light an wrong/missing data entry when a user click "OK"

[yukie]

Where : File -> Preference

Situation : (it can be the same for other items in Preference)
<What I have done>

1. I cleared three "Persons" information, then I entered two of my preference person's names. (One row was empty)
2. pressed "Apply" (An error message has appeared at the top of the table, but I did not notice)
3. switched to other item (e.g. "Role"), and modified the information there (the error message has disappeared)
4. click "OK" to finish Preferences modification

<The result>

5. Nothing happened even the Preferences window was open still.

<To solve this>
I need to check every items in Preferences to see whether I did something wrong or not.. (yes I did, but I did not notice it)

<Wish>
Please pop-up or highlight the position where I made mistake.

[sena]

fixed in revision [2161]