signs aren't ground content

and some whitespace indentation fixes

signs_api/init.lua

@@ -170,6 +170,7 @@ function signs_api.register_sign(mod, name, model)
 					 model.width/2, model.height/2, 0.5 - model.depth},
 		},
 		groups = {choppy=2, dig_immediate=2, not_blocking_trains=1, display_api=1,signs_api_formspec_lbm=1},
+		is_ground_content = false,
 		sounds = default.node_sound_defaults(),
 		display_entities = {
 			["signs:display_text"] = {
@@ -183,21 +184,21 @@ function signs_api.register_sign(mod, name, model)
 		},
 		on_place = display_api.on_place,
 		on_construct = 	function(pos)
-				local ndef = minetest.registered_nodes[minetest.get_node(pos).name]
-				local meta = minetest.get_meta(pos)
-				meta:set_string("font", ndef and ndef.display_entities.font_name or
-				                        font_api.get_default_font_name())
-				signs_api.set_formspec(pos)
-				display_api.on_construct(pos)
-			end,
+			local ndef = minetest.registered_nodes[minetest.get_node(pos).name]
+			local meta = minetest.get_meta(pos)
+			meta:set_string("font", ndef and ndef.display_entities.font_name or
+						font_api.get_default_font_name())
+			signs_api.set_formspec(pos)
+			display_api.on_construct(pos)
+		end,
 		on_destruct = display_api.on_destruct,
 		on_blast = display_api.on_blast,
 		on_rotate = signs_api.on_rotate,
 		on_receive_fields =  signs_api.on_receive_fields,
 		on_punch = function(pos, node, player, pointed_thing)
-				signs_api.set_formspec(pos)
-				display_api.update_entities(pos)
-			end,
+			signs_api.set_formspec(pos)
+			display_api.update_entities(pos)
+		end,
 	}
 
 	-- Node fields override