check if property exists in oozie workflow EL

Question

I am trying to set a property based on the existence of another property in an oozie workflow.xml like this:

<global>
    <configuration>
        <property>
            <name>outputTableName</name>
            <value>${firstNotNull(inputTableName, outputTableOverride)}</value>
        </property>
    </configuration>
</global>

But, outputTableOverride only exists in some cases. Therefore, it fails as it is sometimes missing. Is there a way to check if the property exists?

Discountenance