Removed all uses of 'Blank' unit.

Sea Serpent event now uses a moveto event, and the trapped triton uses
a triton unit.

Fixed the coordinate error in the shipwreck treasure event.

data/campaigns/Under_the_Burning_Suns/scenarios/11_Battle_for_Zocthanol_Isle.cfg

@@ -531,22 +531,13 @@
 
         {PLACE_IMAGE scenery/wreck.png 13 9}
 
-        [unit]
-            type=Blank
-            description="Hidden Serpent"
-            # user description not needed, unit never seen
-            x,y=13,9
-            side=2
-            ai_special=guardian
-        [/unit]
-
         # trapped merman in cage
 
         {PLACE_IMAGE units/merfolk/triton.png 10 5}
         {PLACE_IMAGE items/cage.png 10 5}
 
         [unit]
-            type=Blank
+            type=Merman Triton
             description="Trapped Merman"
             user_description= _ "Trapped Merman"
             x,y=10,5
@@ -1759,21 +1750,18 @@
     # Event 13: Player gets close to wrecked ship
 
     [event]
-        name=sighted
+        name=moveto
 
         [filter]
-            description=Hidden Serpent
-        [/filter]
-
-        [filter_second]
             side=1
-        [/filter_second]
-
-        [kill]
-            description=Hidden Serpent
-            animate=no
-            fire_event=no
-        [/kill]
+            [filter_location]
+		            radius=5 
+		            x,y=13,9
+		            [filter_radius]
+		                terrain=W*
+		            [/filter_radius]
+		        [/filter_location]
+        [/filter]
 
         {UNIT_T (Sea Serpent) (Sea Serpent) ( _ "Sea Serpent") 2 13 9}
         # wmllint: recognize Sea Serpent
@@ -1839,7 +1827,7 @@
         name=moveto
 
         [filter]
-            x,y=13,10
+            x,y=13,9
             side=1
         [/filter]
 

data/campaigns/Under_the_Burning_Suns/units/Blank.cfg

@@ -1,25 +0,0 @@
-#textdomain wesnoth-utbs
-# This is a dummy unit which is used occasionally
-# when I need an invisible unit. It never actually participates in combat.
-[unit]
-    id=Blank
-    name= _ "Blank"
-    race=monster
-    image="blank.png"
-    hitpoints=10
-    movement_type=smallfoot
-    [movement_costs]
-        deep_water=100
-        shallow_water=100
-        grassland=100
-        sand=100
-    [/movement_costs]
-    movement=1
-    experience=100
-    level=0
-    alignment=neutral
-    advanceto=null
-    cost=10
-    usage=fighter
-    hide_help=true
-[/unit]