Fixes bubble/hull shield generators not updating air zones, update_nearby_tiles() cleanup.

code/modules/shieldgen/energy_field.dm

@@ -13,6 +13,14 @@
 	var/strength = 0
 	var/ticks_recovering = 10
 
+/obj/effect/energy_field/New()
+	..()
+	update_nearby_tiles()
+
+/obj/effect/energy_field/Del()
+	update_nearby_tiles()
+	..()
+
 /obj/effect/energy_field/ex_act(var/severity)
 	Stress(0.5 + severity)
 
@@ -44,12 +52,16 @@
 		strength = 0
 
 	//if we take too much damage, drop out - the generator will bring us back up if we have enough power
+	var/old_density = density
 	if(strength >= 1)
 		invisibility = 0
 		density = 1
 	else if(strength < 1)
 		invisibility = 101
 		density = 0
+	
+	if (density != old_density)
+		update_nearby_tiles()
 
 /obj/effect/energy_field/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
 	//Purpose: Determines if the object (or airflow) can pass this atom.