I first make sure the render is paused, then close the Viewport Window, then close the Render setup window.
Then if I select close scene or close window the error dialog comes up, then Modo quits.
I tried repeating this several times. On one occasion, Modo did not crash.
I've looked into this issue in more detail. The message "The scene being rendered in the Viewport has been closed in Modo....." is erroneously being displayed if the Viewport is closed, which I will fix. However I have been unable to replicate a crash. Some questions...
1) Are you on SR4 of Modo7?
2) Does is happen on all scenes?
3) Does it happen if you close the current scene whilst the Viewport is open?
4) What other plugins do you have installed?
5) It a long-shot, but there could be something in your Modo701.cfg file causing the issue. If you rename this file then start Modo, authenticate the plugin, the render and close the scene, does the crash happen? Rename the file back to Modo701.cfg to return to you previous settings once trying this.
6) Just to confirm - when you saying Modo is crashing, you mean it is terminating?
Paul