Already removed runtime folder, but not luck!
Google and got solution:
The cause is xdebug.
XDebug settings in php.ini which crash Debug panel
[XDebug]
zend_extension = "C:\xampp\php\ext\php_xdebug.dll" ;you can keep this line
xdebug.remote_enable = 1
xdebug.remote_host = "127.0.0.1"
xdebug.remote_autostart=on
Commenting or removing this settings restores stable working of debug extension.