wp-cli/wp-cli — pull request #1351 by danielbachhuber (2014-08-21 14:37:50+00:00)
Title: Allow themes and plugins to be listed with `update_version`

When there's no `update_version` available, the attribute is `null` on the
plugin info array.
`isset()` returns false for null values, but `array_key_exists()` and
`property_exists()` do the job

See https://github.com/wp-cli/wp-cli/issues/1166#issuecomment-52911998