preserve inventory order in AHuman::EquipFirearm

This prevents AIs from messing up the inventory order whenever a player switches away from a unit while holding a tool or something.

This has been bugging me for months.

Author: Architector4

Source/Entities/AHuman.cpp

@@ -648,16 +648,19 @@ bool AHuman::EquipFirearm(bool doEquip) {
 		// Found proper device to equip, so make the switch!
 		if (pWeapon && pWeapon->IsWeapon()) {
 			if (doEquip) {
-				// Erase the inventory entry containing the device we now have switched to
-				*itr = 0;
-				m_Inventory.erase(itr);
-
 				// Put back into the inventory what we had in our hands, if anything
 				if (HeldDevice* heldDevice = m_pFGArm->GetHeldDevice()) {
 					heldDevice->Deactivate();
 					AddToInventoryBack(m_pFGArm->RemoveAttachable(heldDevice));
 				}
 
+				// We want to preserve inventory order, so rotate it to the device in question.
+				std::rotate(m_Inventory.begin(), itr, m_Inventory.end());
+
+				// Erase the inventory entry containing the device we now have switched to
+				*m_Inventory.begin() = 0;
+				m_Inventory.pop_front();
+
 				// Now put the device we were looking for and found into the hand
 				m_pFGArm->SetHeldDevice(pWeapon);
 				// Move the hand to a poisition so it looks like the new device was drawn from inventory
@@ -670,6 +673,7 @@ bool AHuman::EquipFirearm(bool doEquip) {
 				if (m_DeviceSwitchSound) {
 					m_DeviceSwitchSound->Play(m_Pos);
 				}
+
 			}
 
 			return true;