In C++14, bool -> T* implicit conversions are not allowed anymore.
See also: https://bugs.gentoo.org/show_bug.cgi?id=598639

--- a/src/interface/weapon_menu.cpp
+++ b/src/interface/weapon_menu.cpp
@@ -391,7 +391,7 @@
 Weapon * WeaponsMenu::UpdateCurrentOverflyItem(const Polygon * poly)
 {
   if (!show)
-    return false;
+    return NULL;
   const std::vector<PolygonItem *>& items = poly->GetItem();
   WeaponMenuItem * tmp;
   Interface::GetInstance()->SetCurrentOverflyWeapon(NULL);