Add null unit checks for SFX and Effects

Remove unused code from Scales

src/singletons/effect.gd

@@ -47,6 +47,11 @@ func create_simple(effect_path: String, effect_pos: Vector2) -> int:
 # follow the unit if it moves.
 # NOTE: Effect.createSimpleAtUnit() in JASS
 func create_simple_at_unit(effect_path: String, unit: Unit, body_part: Unit.BodyPart = Unit.BodyPart.CHEST, z_offset: float = 0.0) -> int:
+	if unit == null:
+		push_error("null unit passed to Effect.create_simple_at_unit()")
+
+		return create_animated(effect_path, Vector3.ZERO, 0.0)
+
 	var effect_pos: Vector3 = unit.get_body_part_position(body_part)
 	effect_pos.z += z_offset
 
@@ -57,6 +62,11 @@ func create_simple_at_unit(effect_path: String, unit: Unit, body_part: Unit.Body
 # if it moves. The effect will also go away if the unit dies.
 # NOTE: Effect.createSimpleOnUnit() in JASS
 func create_simple_at_unit_attached(effect_path: String, unit: Unit, body_part: Unit.BodyPart = Unit.BodyPart.CHEST, z_offset: float = 0.0) -> int:
+	if unit == null:
+		push_error("null unit passed to Effect.create_simple_at_unit_attached()")
+
+		return create_animated(effect_path, Vector3.ZERO, 0.0)
+
 	var effects_container: Node = get_tree().get_root().get_node_or_null("GameScene/World/EffectsContainer")
 
 	if effects_container == null:

src/singletons/sfx.gd

@@ -80,6 +80,11 @@ func sfx_at_pos(sfx_path: String, sfx_position: Vector2, volume_db: float = 0.0,
 # SFXAtUnit() from JASS creates a "simple effect" (SFX),
 # where "effect" is visual, not sound.
 func sfx_at_unit(sfx_path: String, unit: Unit, volume_db: float = 0.0, pitch_scale: float = 1.0):
+	if unit == null:
+		push_error("null unit passed to SFX.sfx_at_unit()")
+
+		return
+
 	var sfx_position: Vector2 = unit.get_visual_position()
 	sfx_at_pos(sfx_path, sfx_position, volume_db, pitch_scale)
 

src/towers/tower_behaviors/scales.gd

@@ -173,13 +173,6 @@ func on_tower_details() -> MultiboardValues:
 	return multiboard
 
 
-# func example_pt_on_hit(p: Projectile, target: Unit):
-# 	if target == null:
-# 		return
-
-# 	tower.do_spell_damage(target, 123, tower.calc_spell_crit_no_bonus())
-
-
 # NOTE: "overchargeA()" in original script
 func mock_eye_glare_st_on_damage(event: Event, _dummy: SpellDummy):
 	var target: Unit = event.get_target()