Few issues, solved.

code/datums/diseases/transformation.dm

@@ -20,11 +20,11 @@
 
 /datum/disease/transformation/Copy()
 	var/datum/disease/transformation/D = ..()
-	D.stage1 = stage1.Copy()
-	D.stage2 = stage2.Copy()
-	D.stage3 = stage3.Copy()
-	D.stage4 = stage4.Copy()
-	D.stage5 = stage5.Copy()
+	D.stage1 = stage1?.Copy()
+	D.stage2 = stage2?.Copy()
+	D.stage3 = stage3?.Copy()
+	D.stage4 = stage4?.Copy()
+	D.stage5 = stage5?.Copy()
 	D.new_form = D.new_form
 	return D
 

code/modules/integrated_electronics/subtypes/manipulation.dm

@@ -78,7 +78,7 @@
 				for(var/i in 1 to length(harvest_output))
 					harvest_output[i] = WEAKREF(harvest_output[i])
 
-				if(harvest_output.len)
+				if(length(harvest_output))
 					set_pin_data(IC_OUTPUT, 1, harvest_output)
 					push_data()
 			if(1)

code/modules/mob/living/carbon/human/species_types/jellypeople.dm

@@ -42,9 +42,10 @@
 		slime_change.Grant(C)	//CIT CHANGE
 	C.faction |= "slime"
 
-/datum/species/jelly/handle_mutant_bodyparts(mob/living/carbon/human/H)
+/datum/species/jelly/handle_body(mob/living/carbon/human/H)
+	. = ..()
 	//update blood color to body color
-	H.dna.species.exotic_blood_color = "#" + H.dna.features["mcolor"]
+	exotic_blood_color = "#" + H.dna.features["mcolor"]
 
 /datum/species/jelly/spec_life(mob/living/carbon/human/H)
 	if(H.stat == DEAD || HAS_TRAIT(H, TRAIT_NOMARROW)) //can't farm slime jelly from a dead slime/jelly person indefinitely, and no regeneration for blooduskers
@@ -539,7 +540,7 @@
 		H.update_body()
 
 	else if (select_alteration == "Markings")
-		var/list/snowflake_markings_list = list()
+		var/list/snowflake_markings_list = list("None")
 		for(var/path in GLOB.mam_body_markings_list)
 			var/datum/sprite_accessory/mam_body_markings/instance = GLOB.mam_body_markings_list[path]
 			if(istype(instance, /datum/sprite_accessory))
@@ -550,8 +551,6 @@
 		new_mam_body_markings = input(H, "Choose your character's body markings:", "Marking Alteration") as null|anything in snowflake_markings_list
 		if(new_mam_body_markings)
 			H.dna.features["mam_body_markings"] = new_mam_body_markings
-			if(new_mam_body_markings == "None")
-				H.dna.features["mam_body_markings"] = "Plain"
 		for(var/X in H.bodyparts) //propagates the markings changes
 			var/obj/item/bodypart/BP = X
 			BP.update_limb(FALSE, H)

code/modules/shuttle/shuttle_creation/shuttle_creator_console.dm

@@ -58,7 +58,7 @@
 	. = ..()
 	owner_rsd.overlay_holder.remove_client()
 	eyeobj.invisibility = INVISIBILITY_MAXIMUM
-	if(user.client)
+	if(user?.client)
 		user.client.images -= eyeobj.user_image
 
 /obj/machinery/computer/camera_advanced/shuttle_creator/attack_hand(mob/user)

code/modules/shuttle/shuttle_creation/shuttle_creator_overlay.dm

@@ -12,8 +12,9 @@
 	holder.images += images
 
 /datum/shuttle_creator_overlay_holder/proc/remove_client()
-	holder.images -= images
-	holder = null
+	if(holder)
+		holder.images -= images
+		holder = null
 
 /datum/shuttle_creator_overlay_holder/proc/clear_highlights()
 	if(holder)