Fixed RasPi builds of unit tests.

On RasPi with gcc 4.8.2, the asserts wouldn't compile when tests were enabled.
Enforced the assumption that ASSERT code is generated only in Debug builds.

src/Entities/ProjectileEntity.cpp

@@ -357,7 +357,9 @@ AString cProjectileEntity::GetMCAClassName(void) const
 		case pkFishingFloat:  return "";  // Unknown, perhaps MC doesn't save this?
 	}
 	ASSERT(!"Unhandled projectile entity kind!");
-	return "";
+	#ifndef __clang__
+		return "";
+	#endif
 }