Fix nil item exception and node particle texture

shooter.lua

@@ -20,7 +20,7 @@ local timer = 0
 local shots = {}
 
 local function spawn_particles(p, v, d, texture)
-	if texture.type ~= "string" then
+	if type(texture) ~= "string" then
 		texture = SHOOTER_EXPLOSION_TEXTURE
 	end
 	local pos = vector.add(p, vector.multiply(v, {x=d, y=d, z=d}))
@@ -55,9 +55,7 @@ local function punch_node(pos, def)
 		return
 	end
 	local item = minetest.registered_items[node.name]
-	if not item.groups then
-		return
-	end
+	if item and item.groups then
 		for k, v in pairs(def.groups) do
 			local level = item.groups[k] or 0
 			if level >= v then
@@ -77,6 +75,7 @@ local function punch_node(pos, def)
 				break
 			end
 		end
+	end
 end
 
 function shooter:fire_weapon(user, pointed_thing, def)