Don't guard against touch: [].

Closes #27683.

Seeing a code sample that leads to what we're guarding against:

```ruby
Topic.update_counters(1, replies_count: 1, touch: [])
```

It doesn't look like a case people would ever intentionally end
up with. Thus we're better off sparing the conditional.

Note: it could happen if a method returns an empty array
that's then passed to `update_counters` and its touchy friends.
But `[].presence` can fix that once people see their query blow
up.

[ Eugene Kenny & Kasper Timm Hansen ]

activerecord/lib/active_record/counter_cache.rb

@@ -105,8 +105,7 @@ module ActiveRecord
         end
 
         if touch
-          touch_updates = touch_updates(touch)
-          updates << sanitize_sql_for_assignment(touch_updates) unless touch_updates.empty?
+          updates << sanitize_sql_for_assignment(touch_updates(touch))
         end
 
         unscoped.where(primary_key => id).update_all updates.join(", ")