If the user moves, renames or deletes the shell icon in SYS:System, a shell/console will crash if you iconify it. If you ignore the DSI in grim reaper the system continues but the the shell is apprently left in an iconified state with no way to reopen it.
In several personal reaction programs I've written; when IIcon->GetDiskObject() fails to find the program icon then calling IIntuition->IDoMethod(winObj, WM_ICONIFY, NULL) will use the a default icon (def_window). Apparently, shell/console windows are being iconified in a way that doesn't automatically supply a default icon and the shell/console code may need to manually check for the presence of the desired icon and use the default icon (def_window) if it's not found.
It's unlikely that a user might move, rename or delete the shell icon in SYS:System but potential crashes should be avoided and fixed.