A couple buildmode fixes

The runtime when not placing a valid path is now replaced with a warning
message

The HUD icon for buildmode is no longer covered up by item actions

code/_onclick/hud/_defines.dm

@@ -161,3 +161,8 @@
 //1 = standard hud
 //2 = reduced hud (just hands and intent switcher)
 //3 = no hud (for screenshots)
+
+
+#define HUD_LAYER_SCREEN 20
+
+#define HUD_LAYER_BUILDMODE 30

code/_onclick/hud/screen_objects.dm

@@ -9,7 +9,7 @@
 /obj/screen
 	name = ""
 	icon = 'icons/mob/screen_gen.dmi'
-	layer = 20
+	layer = HUD_LAYER_SCREEN
 	plane = HUD_PLANE
 	unacidable = 1
 	var/obj/master = null	//A reference to the object in the slot. Grabs or items, generally.

code/datums/action.dm

@@ -127,7 +127,7 @@
 			var/obj/item/I = target
 			var/old_layer = I.layer
 			var/old_plane = I.plane
-			I.layer = 21
+			I.layer = HUD_LAYER_SCREEN + 1
 			I.plane = HUD_PLANE
 			current_button.overlays += I
 			I.layer = old_layer

code/modules/admin/buildmode.dm

@@ -14,6 +14,7 @@
 /obj/screen/buildmode
 	icon = 'icons/misc/buildmode.dmi'
 	var/datum/click_intercept/buildmode/bd
+	layer = HUD_LAYER_BUILDMODE
 
 /obj/screen/buildmode/New(bld)
 	..()
@@ -78,6 +79,7 @@
 /obj/effect/buildmode_reticule
 	var/image/I
 	var/client/cl
+	anchored = TRUE
 
 /obj/effect/buildmode_reticule/New(var/turf/t, var/client/c)
 	loc = t
@@ -454,10 +456,12 @@
 					var/turf/T = get_turf(object)
 					log_admin("Build Mode: [key_name(user)] modified [T] ([T.x],[T.y],[T.z]) to [objholder]")
 					T.ChangeTurf(objholder)
-				else
+				else if(!isnull(objholder))
 					var/obj/A = new objholder (get_turf(object))
 					A.setDir(build_dir)
 					log_admin("Build Mode: [key_name(user)] modified [A]'s ([A.x],[A.y],[A.z]) dir to [build_dir]")
+				else
+					to_chat(user, "<span class='warning'>Select object type first.</span>")
 			else if(right_click)
 				if(isobj(object))
 					log_admin("Build Mode: [key_name(user)] deleted [object] at ([object.x],[object.y],[object.z])")