No PD interception after all launching ships destroyed

[gbum1113]

Describe the bug PD does not acquire and engage active missiles (HEKV-1 at least in my trials) missiles from ships that have been destroyed

To Reproduce

1. get a ship (lets name it A)
2. fire a missile at another ship (lets name it B)
3. fire a railgun from ship B into ship A to kill it
4. missile is no longer properly intercepted

[josuenos]

This issue has been fixed in the dev branch, that fix will be out in the next release.