Nullpointer exception when reconnecting to JOC after shutdown

Current Situation

When the JOC Cockpit Sercice restarts after a shuts down while a session is open, a null pointer exception is shown. After a new login JOC Cockpit works as expected.

To reproduce

• Login in to JOC Cockpit
• Shutdown JOC Cockpit Server
• Wait until JOC Cockpit is started completly
• Reload the JOC Cockpit page
  • A null pointer exception is shown.

Desired Behavior

Instead of a null pointer exception a valid error message should be shown.
Session is broken and no longer valid. New login neccessary