Fix null reference exception during "kpm pack --runtime"

parent #684 
Looking at the codes for `PackRuntime`, it seems to be that there's a more systemic problem: that class has an *optional* `Report` property, yet it will throw `NullRef` exceptions if it isn't set. If the `Report` property is truly required, it should be a constructor parameter. If it's not required, then there should be null checks throughout the code.