CBasePlayerWeapon::SecondaryAmmoIndex should always return m_iSecondaryAmmoType

[SamVanheer]

The method CBasePlayerWeapon::SecondaryAmmoIndexshould always returnm_iSecondaryAmmoType`.

Currently this returns -1, and the MP5 overrides it to return m_iSecondaryAmmoType.

For all other weapons m_iSecondaryAmmoType is initialized to -1 anyway:

halflife/dlls/weapons.cpp

Line 801 in c7240b9

m_iSecondaryAmmoType = pPlayer->GetAmmoIndex( pszAmmo2() );

Changing it to return m_iSecondaryAmmoType does not change the value returned in vanilla Half-Life code.

This can result in inconsistent behavior when making custom weapons. A modder that is unaware of this could end up with bugs and even crashes if the index is used to get the player's current remaining ammo since -1 is out of bounds.

With this change, if pszAmmo2() returns a non-null pointer it is safe to assume that SecondaryAmmoIndex also returns a valid index.