Add Substitute to a Schedule should work from Resources tab

Current Situation

• When users try to use the "Add Substitute" action to a Schedule from the Resources view of JOC Cockpit then the substitute is not added and the Schedule configuration becomes empty for the Schedule that is added as a Substitute.

How to Reproduce

• Create two Schedules from the JOC Cockpit Configuration view (schedule1 and schedule2)
• Switch to the Resources view of the JOC Cockpit
• Click on the action menu of schedule1 and select "Add Substitute".
• Select schedule2 from the list and add it as a substitute.
• The schedule2 is not added as a substitute and also the configuration of schedule2 is changed to

  <schedule />
  

Desired Behavior

• The operation "Add Substitute" to a Schedule should work from the Resources view.