Merge branch 'github'

Ethereal clears every biome when it starts to get rid of the default mapgen, which breaks the nether and can cause crashes.
Adding Ethereal as an optional dependency ensures the nether is loaded after Ethereal has already cleared the biomes.

init.lua

@@ -155,7 +155,7 @@ This opens to a truly hellish place, though for small mercies the air there is s
 The expedition parties have found no diamonds or gold, and after an experienced search party failed to return from the trail of a missing expedition party, I must conclude this is a dangerous place.]], 10 * nether.FASTTRAVEL_FACTOR),
 
 		is_within_realm = function(pos) -- return true if pos is inside the Nether
-			return pos.y < nether.DEPTH_CEILING
+			return pos.y < nether.DEPTH_CEILING and pos.y > nether.DEPTH_FLOOR
 		end,
 
 		find_realm_anchorPos = function(surface_anchorPos, player_name)

mod.conf

@@ -1,4 +1,4 @@
 name = nether
 description = Adds a deep underground realm with different mapgen that you can reach with obsidian portals.
 depends = stairs, default
-optional_depends = moreblocks, mesecons, loot, dungeon_loot, doc_basics, fire, climate_api
+optional_depends = moreblocks, mesecons, loot, dungeon_loot, doc_basics, fire, climate_api, ethereal

nodes.lua

@@ -529,7 +529,7 @@ minetest.register_node("nether:lava_crust", {
 	paramtype = "light",
 	light_source = default.LIGHT_MAX - 3,
 	buildable_to = false,
-	walkable_to = true,
+	walkable = true,
 	is_ground_content = true,
 	drop = {
 		items = {{

portal_api.lua

@@ -2015,7 +2015,6 @@ local wormhole_nodedef_default = {
 	is_ground_content = false,
 	drop = "",
 	light_source = 5,
-	alpha = 192,
 	node_box = {
 		type = "fixed",
 		fixed = {