Item dupe: Dropping weapons you don't have

[geist22]

Since we don't already have an issue about this, I thought I'd open one myself before it gets forgotten. Original game issue, found by rafalyp73 as explained in a comment on https://www.youtube.com/watch?v=S8QY-dNRQQ8.

Agents can be made to drop items they don't have.

To reproduce:

1. Agent 1 has an Uzi, agent 2 has a Minigun
2. Click left or right (doesn't matter) on agent 1's Uzi and hold the mouse button down
3. While holding the click, move the cursor over agent 2's Minigun, then press the other button

Result: Agent 1 drops a Minigun, even if he doesn't have one.