force all signs into the sign group

api.lua

@@ -22,11 +22,9 @@ signs_lib.standard_yoffs = 0
 signs_lib.standard_cpl = 35
 
 signs_lib.standard_wood_groups = table.copy(default and minetest.registered_items["default:sign_wall_wood"].groups or {})
-signs_lib.standard_wood_groups.sign = 1
 signs_lib.standard_wood_groups.attached_node = nil
 
 signs_lib.standard_steel_groups = table.copy(default and minetest.registered_items["default:sign_wall_steel"].groups or {})
-signs_lib.standard_steel_groups.sign = 1
 signs_lib.standard_steel_groups.attached_node = nil
 
 signs_lib.standard_wood_sign_sounds  = table.copy(default and minetest.registered_items["default:sign_wall_wood"].sounds or {})
@@ -167,7 +165,13 @@ minetest.register_entity("signs_lib:text", {
 	mesh = "signs_lib_standard_sign_entity_wall.obj",
 	textures = {},
 	static_save = true,
-	backface_culling = false
+	backface_culling = false,
+	on_activate = function(self)
+		local node = minetest.get_node(self.object:get_pos())
+		if minetest.get_item_group(node.name, "sign") == 0 then
+			self.object:remove()
+		end
+	end,
 })
 
 function signs_lib.delete_objects(pos)
@@ -722,6 +726,7 @@ end
 function signs_lib.rightclick_sign(pos, node, player, itemstack, pointed_thing)
 
 	if not player or not signs_lib.can_modify(pos, player) then return end
+	if not player.get_meta then return end
 
 	player:get_meta():set_string("signslib:pos", minetest.pos_to_string(pos))
 	minetest.show_formspec(player:get_player_name(), "signs_lib:sign", get_sign_formspec(pos, node.name))
@@ -1022,6 +1027,9 @@ function signs_lib.register_sign(name, raw_def)
 		def.groups = signs_lib.standard_wood_groups
 	end
 
+	-- force all signs into the sign group
+	def.groups.sign = def.groups.sign or 1
+
 	local cbox = signs_lib.make_selection_boxes(35, 25)
 
 	def.selection_box = raw_def.selection_box or cbox