Adani enterprise 05-06 September drop

On 6th september Adani ent. dropped 22.4 % due to demerger of gas business . it was announced that holder of stocks of umbrella co. will be getting 1 share of Adani gas once it was listed .
My question is what happened to those fellas who had overnight position in F&O in the long side . According to calculation ,loss will be 22.4 *X (x being leverage multiplier ) % wiped out of their margin .
Or am i missing something .
If that is the case hoe to escape such type of situation(merger,demerger,bonus share issue news ) , kindly advise .

I think all FNO were auto squared off one day before that

@d_k ; Similar process will be there in CESC which will last trade as combined entity on October 29 and last day for all in built f& o positions . share will undergo price discovery without other 2 entities ( CESC being d-merged in 3 companies ) on October 30 and accordingly fresh strike price and so fresh positions have to be built if desired.