Crash with divide by zero when teleporting to earth level

[Riot]

Caused by std::cout << static_cast<int>(parent->mass_destroyed / parent->initial_mass * 100) << "% destroyed" << std::endl;

[Riot]

safety check to avoid division by zero on debris destruction info message, resolves #189

→ <<cset c73f6c8372f9>>

[Riot]

adding asteroid mass destroyed announcements, re #189

→ <<cset bf3a9a18d093>>

[Riot]

Removing milestone: Beta (automated comment)