Use childful transforms as displayable

that's not *explicitly* documented, but it won't change any time soon
also deletes a placeholder image

(cherry picked from commit 3b6dd38e19)

game/scripts/animations/generator.rpy

@@ -1,6 +1,3 @@
-image object:
-    Null()
-
 transform OBJbutterfly(hue=random.randint(0, 359)):
     zoom random.uniform(0.4, 0.85)
     matrixcolor HueMatrix(hue)

game/scripts/characters/luna/events/spectrespecs/fx.rpy

@@ -60,7 +60,7 @@ screen spectrevision():
     tag spectrevision
 
     for i in range(wrackspurts_count):
-        add "object" at OBJwrackspurt
+        add OBJwrackspurt
 
     add "spectrevision"
 

game/scripts/rooms/quidditch_pitch/init.rpy

@@ -5,7 +5,7 @@ screen quid_pitch_back():
     add "images/rooms/quidditch_pitch/back.webp" zoom 0.5
     if game.weather == "cloudy":
         for i in range(random.randint(2, 5)):
-            add "object" at OBJcloud
+            add OBJcloud
     add "images/rooms/quidditch_pitch/back_overlay.webp" zoom 0.5
 
 screen quid_pitch_mid():
@@ -18,4 +18,4 @@ screen quid_pitch_front():
     zorder 5
     add "images/rooms/quidditch_pitch/front.webp" zoom 0.5
     for i in range(random.randint(1, 3)):
-        add "object" at OBJbutterfly
+        add OBJbutterfly