HttT S19b: Fixed void armor breakage introduced in ef641d6e

Because of the added $unit references, the unit variable got stored before the object's effects were applied, leading to the unstoring of the unit to subsequently overwrite them.

data/campaigns/Heir_To_The_Throne/utils/httt_utils.cfg

@@ -227,11 +227,12 @@
                                     [/message]
                                     {VARIABLE armor_taken 1}
 
-                                    [set_variables]
-                                        name=unit.modifications.trait
-                                        mode=append
+                                    [modify_unit]
+                                        [filter]
+                                            x,y={X},{Y}
+                                        [/filter]
 
-                                        [value]
+                                        [trait]
                                             id=void_armor
                                             name= _ "void armor"
                                             description= _ "The Void Armor grants the following resistances:
@@ -239,13 +240,8 @@ blade:  50%
 pierce: 40%
 impact: 40%
 fire:  +10%"
-                                        [/value]
-                                    [/set_variables]
-
-                                    [unstore_unit]
-                                        variable=unit
-                                        find_vacant=no
-                                    [/unstore_unit]
+                                        [/trait]
+                                    [/modify_unit]
                                 [/then]
                                 #
                                 # Set physical resistance to 50/40/40