SaveFileDialog does not open overwrite confirmation message box if the file name is typed with the default extension at the end.

For example, you have "empty.txt" file on the desktop. You open SaveFileDialog, type empty, select TXT extension on the filters list on the bottom. Remove the .txt from the file name (if it is there) and press Save. 

Expected: Confirmation window for overwriting the file should be opened.

Actual: No confirmation window opens.