DiD S8: Ensure Spectral Servant unit-line cannot pick up the book

Fixes #6576

data/campaigns/Descent_Into_Darkness/scenarios/08_Alone_at_Last.cfg

@@ -949,6 +949,10 @@
             [not]
                 type_adv_tree=Ghost,Vampire Bat
             [/not]
+            [not]
+                # this unit does not advance normally so each type has to be listed individually
+                type=Spectral Servant,Phantom,Eidolon
+            [/not]
         [/filter]
 
         [remove_item]
@@ -998,7 +1002,7 @@
             x=$bookX
             y=$bookY
             side=1
-            type=Ghost,Wraith,Spectre,Shadow,Nightgaunt
+            type=Ghost,Wraith,Spectre,Shadow,Nightgaunt,Spectral Servant,Phantom,Eidolon
         [/filter]
 
         [message]