[OMEdit] Do not allow the simulation window to be closed if the simulation is still running

[Adrian Pop]

For simulations is would be good not to be able to close the simulation window (btw, how do you get it back if you closed it?).

Especially for simulations that give some asserts at initialization but then continue is for the user to tell if the simulation failed or is actually continuing. The user closes the window, does some model modification and then recompiles one would get a "permision denied" when the gcc linker ld tries to write the executable again. OMEdit knows that the exe is still running, it should not let the user recompile the model.