Patch Paranoia#delete to resolve ActiveRecord::ConnectionAdapters::Nu…

…llTransaction errors

Patches Paranoia gem to fix a conflict with transactions in Rspec: rubysherpas/paranoia#274

Example error:
```
Failure/Error: order.line_items.first.variant.tap(&:delete)
NoMethodError:
       undefined method `state' for #<ActiveRecord::ConnectionAdapters::NullTransaction:0x0000564117dddd18>
```

config/initializers/paranoia.rb

@@ -4,7 +4,7 @@ def paranoia_delete
     if persisted?
       # if a transaction exists, add the record so that after_commit
       # callbacks can be run
-      add_to_transaction
+      add_to_transaction unless self.class.connection.current_transaction.closed?
       update_columns(paranoia_destroy_attributes)
     elsif !frozen?
       assign_attributes(paranoia_destroy_attributes)