Display the right text for Valkyrie weapon tooltip

```
It would display the damage followed by "(null)" for no upgrades.
This fix it.
```

Original issue reported on code.google.com by `undeadga...@free.fr` on 24 Feb 2015 at 5:27

Attachments:
- [weapon_armor_tooltip.cpp.patch](https://storage.googleapis.com/google-code-attachments/gptp/issue-36/comment-0/weapon_armor_tooltip.cpp.patch)
