Fix RevolverBarrelComponent ExposeData not checking if serializer is reading

Content.Server/GameObjects/Components/Weapon/Ranged/Barrels/RevolverBarrelComponent.cs

@@ -42,8 +42,15 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged.Barrels
         {
             base.ExposeData(serializer);
             serializer.DataField(ref _caliber, "caliber", BallisticCaliber.Unspecified);
+
+            if (serializer.Reading)
+            {
                 var capacity = serializer.ReadDataField("capacity", 6);
                 _ammoSlots = new IEntity[capacity];
+            }
+
+            // TODO: Writing?
+
 
             // Sounds
             serializer.DataField(ref _soundEject, "soundEject", "/Audio/Guns/MagOut/revolver_magout.ogg");