Getting "Index was out of Range.Must be Non negative" exception in ui explorer

Hi All,

i am trying to capture text which is present on alert pop up("Birth Date is lessthan 21 years).When i am trying to capture this text by clicking on “indicate element” i am getting “Index was out of Range.Must be Non negative” exception.i am using get attribute activity to capture inner text from this popup.Can some one help me in resolving this issue pls.Here are the screenshots.

Can some one pls respond to this?Though i have selected limited text (Birth Date Lessthan 21 years) getting this exception.Thanks in advance