Server fails to start since extension.store.uri is not defined in startup.properties

If the following property is left blank :

HDFS location of extension store for extension artifacts
*.extension.store.uri=

Then falcon fails to start saying extension uri to be defined. I have to explicitly remove it along with org.apache.falcon.extensions.ExtensionService from application services.

These should be handled and falcon should not fail to start in absence of these properties.