You WILL be turned around and sent home if there is no space in your passport to affix the visa sticker.
You also potentially (though unlikely) face prosecution and/or a ban from travel to India for making a false statement in the application that you had the required empty pages available.
Also keep in mind that if you get a new passport issued (as opposed to additional pages), you will need to reapply for the visa online as the previously approved eVisa is linked to the passport number.