SmxKernelPlatform$GuardClassLoader.loadClass() fails when class is in the default package

The folliwing line:

pkg = name.substring(0, name.lastIndexOf('.'));

fails when name represents a class in the default package and makes String.substring() throw ad ArrayIndexOutOfBoundsException.

Attached is a simple fix. I guess you can make it look better

Patch is against current trunk.