[CPP] Fix non-equipment items can cause map crash

[ampitere]

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What does this pull request do?

Currently since CLuaBaseEntity::canEquipItem only takes an item ID as a param then casts it, it will sometimes be a non-equipment item. With the addition of isEquippableByRace it attempts to check a modifier that doesn't exist on non-equipment items. To fix this we'll add a return false if the item is not equipment. Resolves #5703

Steps to test these changes

1. Go to a conquest NPC
2. Keep opening the "Are you sure you want to purchase the X?" menu on a non-equipment item (Scroll of Instant Warp for example)

[WinterSolstice8]

Just to be sure -- you also checked ranged weapons, ammo, shields, things that aren't weapons but are equippable in ammo, etc?

I'm sure it works based on the set type/get type functions

void CItem::setType(uint8 type)
{
    m_type |= type;
}

bool CItem::isType(ITEM_TYPE type) const
{
    return (m_type & type);
}

all of those things should be under "CItemEquipment" but this GetType junk is a bit unknown to me

[ampitere]

Just to be sure -- you also checked ranged weapons, ammo, shields, things that aren't weapons but are equippable in ammo, etc?

I'm sure it works based on the set type/get type functions

void CItem::setType(uint8 type)
{
    m_type |= type;
}

bool CItem::isType(ITEM_TYPE type) const
{
    return (m_type & type);
}

all of those things should be under "CItemEquipment" but this GetType junk is a bit unknown to me

The cast to CItemEquipment changes the type to EQUIPMENT so if it's not that type then it failed the cast and still has it's previous type as far as I can tell. Shields, ammo, fishing rods, bait, lures, guns, bows, etc. are all in item_equipment.sql so those all should properly cast to equipment.