Please consider supporting a default value for parameters if they are empty or unset. There are cases where env parameters ${ENV, var="SOME_ENV_VAR"} are not set. And for build parameters there can be the case when it is not set at all. For example, this happens with Groovy scripts that trigger builds, see e.g. JENKINS-13768

In these cases it would be nice to be able to print something instead of the empty string. For env vars this seems easy, as it's just another parameters then: ${ENV, var="SOME_ENV_VAR", ifUnset="[not set]"}". For build parameters it might be more tricky, but the the same concept might apply. And since they end up in env variables anyway, one workaround would be simply using ${ENV, var="MyBuildParameter", ifUnset="[not set]"}.