Fix FixAmmoSelling causing invisible pickups

Non-default value of pickup class was used to
spawn pickup when player drops a weapon.
But since we've replaced that class and it doesn't
(or might not) exist on the client - dropped weapons
appeared as invisible.

Catch the moment our custom pickup is spawned and
replace it back with default one.

sources/Features/FixAmmoSelling/FixAmmoSelling.uc

@@ -170,6 +170,21 @@ public function OnDisabled()
     }
 }
 
+//  Checks if given class is a one of our pickup replacer classes.
+public static final function bool IsReplacer(class<Actor> pickupClass)
+{
+    local int i;
+    if (pickupClass == none) return false;
+    for (i = 0; i < default.rules.length; i += 1)
+    {
+        if (pickupClass == default.rules[i].pickupReplacement)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 //  1. Checks if weapon can be abused and if it can, - fixes the problem.
 //  2. Starts tracking abusable weapon to detect when player buys ammo for it.
 public final function FixWeapon(KFWeapon potentialAbuser)