TSG S7b: use 1.13 code and make it debug safe

The invulnerable status is player-visible and does not insert new events which
are checked at each attack.

[ci skip]

data/campaigns/The_South_Guard/scenarios/07b_Pebbles_in_the_Flood.cfg

@@ -66,7 +66,7 @@
 
         canrecruit=yes
         [ai]
-            passive_leader=yes # So he can't attacked or pinned away from his keep
+            passive_leader=yes # So he can't attack or be pinned away from his keep
             recruitment_pattern=scout, fighter, fighter, archer, scout, fighter, archer
             aggression=1.0
             caution=0.0
@@ -81,9 +81,6 @@
         {FLAG_VARIANT undead}
     [/side]
 
-    # Make it impossible for the player to kill him, no matter how lucky.
-    {FORCE_CHANCE_TO_HIT side=1 id="Mal M'Brin" 0 ()}
-
     [side]
         side=3
         type=Lich
@@ -158,6 +155,16 @@
         {MODIFY_UNIT x,y=24-40,5-25 facing sw}
 
         {CLEAR_VARIABLE stored_side_1}
+
+        # Make it impossible for the player to kill him, no matter how lucky.
+        [modify_unit]
+            [filter]
+                id="Mal M'Brin"
+            [/filter]
+            [status]
+                invulnerable=yes
+            [/status]
+        [/modify_unit]
     [/event]
 
     #start
@@ -298,6 +305,16 @@
             message= _ "We will crush Westin as we have crushed you! No one shall stand between us and our home."
         [/message]
 
+        [endlevel]
+            result=victory
+            bonus=no
+            {NEW_GOLD_CARRYOVER 100}
+        [/endlevel]
+    [/event]
+
+    [event]
+        name=victory
+
         {VARIABLE pebbles_defense_length $turn_number}
 
         [kill]
@@ -314,7 +331,7 @@
             variable=stored_Deoran
         [/unstore_unit]
 
-        #Set the amount of gold that the player has to what it was before Pebbles.
+        # Set the amount of gold that the player has to what it was before Pebbles.
         [modify_side]
             side=1
             gold=$pebbles_starting_gold
@@ -322,10 +339,14 @@
         {CLEAR_VARIABLE pebbles_starting_gold}
         {CLEAR_VARIABLE stored_Deoran}
 
-        [endlevel]
-            result=victory
-            bonus=no
-            {NEW_GOLD_CARRYOVER 100}
-        [/endlevel]
+        # In case that matters if played as MP Campaign, make him vulnerable again
+        [modify_unit]
+            [filter]
+                id="Mal M'Brin"
+            [/filter]
+            [status]
+                invulnerable=no
+            [/status]
+        [/modify_unit]
     [/event]
 [/scenario]