Bug with empty string user_args

You can reproduce this bug by running the following command command

(-user_args ""), which corresponds to JobConf.UserMainArguments

./bin/run_spark.sh -job_id SparkALS -executor_json `pwd`/examples/resources/spark_test_executor_resources.json -user_main edu.snu.nemo.examples.spark.SparkPi -dag_dir "./dag/sparkals" -user_args ""

Exception that I got is:

java.lang.RuntimeException: org.apache.reef.tang.exceptions.InjectionException: Could not invoke constructor: new ClientRPC(TransportFactory = [ClassNodeImpl 'org.apache.reef.wake.remote.transport.netty.MessagingTransportFactory']: org.apache.reef.wake.remote.transport.netty.MessagingTransportFactory(org.apache.reef.wake.remote.address.LocalAddressProvider), = org.apache.reef.wake.remote.transport.netty.MessagingTransportFactory@f14a7d4, LocalAddressProvider = [ClassNodeImpl 'org.apache.reef.wake.remote.address.HostnameBasedLocalAddressProvider']: org.apache.reef.wake.remote.address.HostnameBasedLocalAddressProvider(), = HostnameBasedLocalAddressProvider:127.0.1.1, String ClientSideRPCServerHost = 127.0.1.1, Integer ClientSideRPCServerPort = 13920)
at org.apache.reef.tang.InjectionFuture.get(InjectionFuture.java:127)
at org.apache.reef.tang.implementation.java.InjectorImpl.getInstance(InjectorImpl.java:521)
at org.apache.reef.tang.implementation.java.InjectorImpl.getInstance(InjectorImpl.java:533)
at org.apache.reef.runtime.common.REEFEnvironment.fromConfiguration(REEFEnvironment.java:116)
at org.apache.reef.runtime.common.REEFEnvironment.fromConfiguration(REEFEnvironment.java:69)
at org.apache.reef.runtime.common.REEFLauncher.main(REEFLauncher.java:180)