Removes more unnecessary code

And revert of something that is just adding an unnecessary check by
doing the QDEL_NULL

code/modules/clothing/spacesuits/rig/modules/computer.dm

@@ -163,11 +163,8 @@
 					to_chat(user, "<span class='danger'>You cannot eject your currently stored AI. Purge it manually.</span>")
 				return 0
 			to_chat(user, "<span class='danger'>You purge the remaining scraps of data from your previous AI, freeing it for use.</span>")
-			if(integrated_ai)
-				integrated_ai.ghostize()
-				QDEL_NULL(integrated_ai)
-			if(ai_card)
-				QDEL_NULL(ai_card)
+			QDEL_NULL(integrated_ai)
+			QDEL_NULL(ai_card)
 		else if(user)
 			user.put_in_hands(ai_card)
 		else

code/modules/hydroponics/hydroponics.dm

@@ -442,8 +442,7 @@
 
 /obj/machinery/hydroponics/proc/mutateweed() // If the weeds gets the mutagent instead. Mind you, this pretty much destroys the old plant
 	if( weedlevel > 5 )
-		if(myseed)
-			QDEL_NULL(myseed)
+		QDEL_NULL(myseed)
 		var/newWeed = pick(/obj/item/seeds/liberty, /obj/item/seeds/angel, /obj/item/seeds/nettle/death, /obj/item/seeds/kudzu)
 		myseed = new newWeed
 		dead = 0
@@ -911,7 +910,8 @@
 			plant_health = 0
 			if(harvest)
 				harvest = FALSE //To make sure they can't just put in another seed and insta-harvest it
-			QDEL_NULL(myseed)
+			qdel(myseed)
+			myseed = null
 			plant_hud_set_health()
 			plant_hud_set_status()
 		adjustWeeds(-10) //Has a side effect of cleaning up those nasty weeds

code/modules/mob/living/silicon/robot/robot.dm

@@ -1205,12 +1205,11 @@ var/list/robot_verbs_default = list(
 	canmove = 1
 	scrambledcodes = 1
 	//Disconnect it's camera so it's not so easily tracked.
-	if(src.camera)
-		QDEL_NULL(src.camera)
-		// I'm trying to get the Cyborg to not be listed in the camera list
-		// Instead of being listed as "deactivated". The downside is that I'm going
-		// to have to check if every camera is null or not before doing anything, to prevent runtime errors.
-		// I could change the network to null but I don't know what would happen, and it seems too hacky for me.
+	QDEL_NULL(src.camera)
+	// I'm trying to get the Cyborg to not be listed in the camera list
+	// Instead of being listed as "deactivated". The downside is that I'm going
+	// to have to check if every camera is null or not before doing anything, to prevent runtime errors.
+	// I could change the network to null but I don't know what would happen, and it seems too hacky for me.
 
 /mob/living/silicon/robot/proc/ResetSecurityCodes()
 	set category = "Robot Commands"