Fix incorrect arg in Entity.init

src/entity.zig

@@ -85,7 +85,7 @@ pub fn Entity(comptime ctx: anytype) type {
         /// To set their values you'll need to use `set(...)` on the
         /// `Entity` returned from this function.
         pub fn init(world: *World(ctx), config: Config, ids: anytype) !Self {
-            const meta = @typeInfo(@TypeOf(add));
+            const meta = @typeInfo(@TypeOf(ids));
             if (meta != .Struct or (meta.Struct.is_tuple == false and meta.Struct.fields.len > 0))
                 @compileError("Expected tuple or empty struct, got '" ++ @typeName(@TypeOf(ids)) ++ "'");
             if (meta.Struct.fields.len > c.FLECS_ID_DESC_MAX)