Firstly make sure to go through the college guidelines. Some college might need english to be a compulsory language if the medium of instruction is going to be in English. Make sure if you have got the admission form for the right course. If the problem isnt sorted then leave a mail to the admissions committee.

Almost every education board has English as its core subjects in 12th, that's why the form also has it as a compulsory slot. Since your case is a bit peculiar, you shall contact the administration department of MDI mentioning your case. Otherwise also, if you are filling marks of five subjects in the form, you can try to fill the form by filling zero in the English marks slot. With marks mentioned in other five subjects, they will figure out that it wasn't your compulsory subject. But still I'll suggest you to contact the administration regarding the same.