When starting a Freestyle job that has been parameterized with a Label parameter from the nodelabelparameter plugin, a "Show Nodes" button is visible to the right of the label field. No matter what value is entered into the label field, the warning always appears that a label must be specified.

The label argument to the doXXX method seems to always by the empty string or null. The problem has been seen on plugin versions 1.7.3 (from 2016) through the current release and with multiple Jenkins versions