Can't start CDK server if user or password env var is empty

If the user or password env var name is empty, then server refuses to start. The error is the following:

!ENTRY org.jboss.tools.openshift.cdk.server.core 4 0 2016-09-26 11:29:46.973
!MESSAGE Exec_tty error:Cannot run program "C:\Apps\HashiCorp\Vagrant\bin\vagrant.exe": Unknown reason
!STACK 0
java.io.IOException: Exec_tty error:Cannot run program "C:\Apps\HashiCorp\Vagrant\bin\vagrant.exe": Unknown reason
at org.eclipse.cdt.utils.spawner.Spawner.exec_pty(Spawner.java:387)
at org.eclipse.cdt.utils.spawner.Spawner.<init>(Spawner.java:99)
at org.eclipse.cdt.utils.spawner.ProcessFactory.exec(ProcessFactory.java:98)
at org.jboss.tools.openshift.cdk.server.core.internal.adapter.controllers.VagrantLaunchUtility.callProcess(VagrantLaunchUtility.java:198)
at org.jboss.tools.openshift.cdk.server.core.internal.adapter.controllers.VagrantLaunchUtility.callInteractive(VagrantLaunchUtility.java:185)
at org.jboss.tools.openshift.cdk.server.core.internal.adapter.controllers.VagrantLaunchUtility.callInteractive(VagrantLaunchUtility.java:178)
at org.jboss.tools.openshift.cdk.server.core.internal.adapter.controllers.CDKLaunchController.launch(CDKLaunchController.java:201)
at org.jboss.ide.eclipse.as.wtp.core.server.launch.ControllableServerLaunchConfiguration.launch(ControllableServerLaunchConfiguration.java:52)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:885)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:739)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:731)
at org.eclipse.wst.server.core.internal.Server.startImpl2(Server.java:3556)
at org.eclipse.wst.server.core.internal.Server.startImpl(Server.java:3492)
at org.eclipse.wst.server.core.internal.Server$StartJob.run(Server.java:367)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)