Remove button should be disabled for default JRE in Java Runtime settings dialog

Tested build : 6u10 b24
Tested OS : windows

Steps to reproduce :
1. install 6u10 b24
2. launch java control panel
3. go to java tab, click view button
Java Runtime Settings dialog will be launched. There will be a default JRE entry (installed JRE)
4. select the default JRE
5. Click on Remove button
default JRE entry is removed from the table

Expected behavior: It should not allow to remove the default JRE entry from the table. It is better to disable the Remove button when default JRE is chosen.

Note : It is a regression from b23.