Hello Avik,
I think this popup is occuring while you are trying to close the simulink model 'dMultiSelection.slmx'.
You can use the 'close_system' command with 'saveflag' value of 0 to close the model without saving.
>> close_system('dMultiSelection', 0)
You can refer to the following link for the same:
Also go through the following example on 'Managing Requirements Without Modifying Simulink Model Files':
I hope this helps.
