ModelEditor: Cannot reload model file

Steps to reproduce:

• have a model opened (or just create one)
• save it
  • trigger the menu item for 'Reload "bla.model"'

OR

• change something [add or remove some element(s), change the position of some elements... whatever]
  • trigger the menu item for 'Revert "bla.model" to Saved'

Current result:

• in both cases you'll get an error message box stating that QC cannot reload the model file