Some arguments for UI components are optional, so we don't have to
provide all of them when using them. I had added a `defined?(name)`
check to use default values when an argument is not provided.
Jeremy pointed out that it was working by accident. In the code `name =
defined?(name)`, `defined?(name)` always returns `local-variable`
because it’s on the right-hand side of the assignment, while the local
variable is on the left-hand side.
When we remove the `defined?` calls, the remaining code is equivalent to
`||=`.
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