[moreblocks & ferns] Fix double drops and global variables

- Fix a global variable in mods/moreblocks/stairsplus/init.lua
- Fix double drops of fern trunks and leaves (see #180)

mods/moreblocks/stairsplus/init.lua

@@ -18,7 +18,7 @@ and minetest.setting_getbool("creative_mode") then
 end
 
 function stairsplus:prepare_groups(groups)
-	result = {}
+	local result = {}
 	if groups then
 		for k, v in pairs(groups) do
 			if k ~= "wood" and k ~= "stone" then

mods/plantlife_modpack/ferns/treefern.lua

@@ -67,9 +67,9 @@ minetest.register_node("ferns:tree_fern_leaves", {
 			{
 				items = {"ferns:sapling_tree_fern"},
 			},
-			{
-				items = {"ferns:tree_fern_leaves"},
-			}
+--			{
+--				items = {"ferns:tree_fern_leaves"},
+--			}
 		}
 	},
 	sounds = default.node_sound_leaves_defaults(),
@@ -98,9 +98,9 @@ minetest.register_node("ferns:tree_fern_leaves_02", {
 			{
 				items = {"ferns:sapling_tree_fern"},
 			},
-			{
-				items = {"ferns:tree_fern_leaves"},
-			}
+--			{
+--				items = {"ferns:tree_fern_leaves"},
+--			}
 		}
 	},
 	sounds = default.node_sound_leaves_defaults(),
@@ -135,7 +135,6 @@ minetest.register_node("ferns:fern_trunk", {
         local node = minetest.get_node({x=pos.x,y=pos.y+1,z=pos.z})
         if node.name == "ferns:fern_trunk" then
             minetest.dig_node({x=pos.x,y=pos.y+1,z=pos.z})
-            minetest.add_item(pos,"ferns:fern_trunk")
         end
     end,
 })