Testing/fixes.

code/game/objects/items/devices/scanners/mass_spectrometer.dm

@@ -18,9 +18,9 @@
 
 /obj/item/scanner/spectrometer/on_update_icon()
 	. = ..()
-	icon_state = initial(icon_state)
-	if(reagents.total_volume)
-		icon_state += "_s"
+	icon_state = get_world_inventory_state()
+	if(reagents?.total_volume)
+		icon_state += "_loaded"
 
 /obj/item/scanner/spectrometer/is_valid_scan_target(atom/O)
 	if(!O.reagents || !O.reagents.total_volume)

code/game/objects/items/toys.dm

@@ -89,7 +89,7 @@
 /obj/item/chems/water_balloon/on_update_icon()
 	. = ..()
 	icon_state = get_world_inventory_state()
-	if(reagents?.total_volume < =0)
+	if(reagents?.total_volume <= 0)
 		icon_state = "[icon_state]_empty"
 
 /obj/item/chems/water_balloon/afterattack(obj/target, mob/user, proximity)

code/modules/projectiles/guns/launcher/syringe_gun.dm

@@ -17,8 +17,10 @@
 	. = ..()
 	underlays.Cut()
 	if(syringe)
-		underlays += image(syringe.icon, src, syringe.icon_state)
-		underlays += syringe.filling
+		var/mutable_appearance/MA = syringe.appearance
+		MA.layer = FLOAT_LAYER
+		MA.plane = FLOAT_PLANE
+		underlays += MA
 
 /obj/item/syringe_cartridge/attackby(obj/item/I, mob/user)
 	if(istype(I, /obj/item/chems/syringe) && user.try_unequip(I, src))

code/modules/reagents/reagent_containers/inhaler.dm

@@ -38,7 +38,7 @@
 	. = ..()
 	if(ATOM_IS_OPEN_CONTAINER(src))
 		add_overlay("[icon_state]_loaded")
-	if(reagents.total_volume > 0)
+	if(reagents?.total_volume > 0)
 		add_overlay("[icon_state]_reagents")
 
 /obj/item/chems/inhaler/attack(var/mob/living/carbon/human/target, var/mob/user, var/proximity)

code/modules/reagents/reagent_containers/syringes.dm

@@ -85,14 +85,14 @@
 	if(mode == SYRINGE_BROKEN)
 		icon_state = "[icon_state]_broken"
 		return
-	var/rounded_vol = clamp(round((reagents.total_volume / volume * 15),5), 5, 15)
-	if (reagents.total_volume == 0)
-		rounded_vol = 0
+	var/rounded_vol = 0
+	if (reagents?.total_volume > 0)
+		rounded_vol = clamp(round((reagents.total_volume / volume * 15),5), 5, 15)
 	if(ismob(loc))
 		add_overlay((mode == SYRINGE_DRAW)? "[icon_state]_draw" : "[icon_state]_inject")
 	icon_state = "[icon_state]_[rounded_vol]"
-	if(reagents.total_volume)
-		filling = image(icon, "[icon_state]_underlay")
+	if(reagents?.total_volume)
+		var/image/filling = image(icon, "[icon_state]_underlay")
 		filling.color = reagents.get_color()
 		filling.appearance_flags |= RESET_COLOR
 		underlays += filling