Added filter to mutable set removal to prevent crash in some situations
Added filter to mutable set removal to prevent crash in some situations

xNUTs/MIT-Mobile-for-iOS,smartcop/MIT-Mobile-for-iOS,MIT-Mobile/MIT-Mobile-for-iOS,xNUTs/MIT-Mobile-for-iOS,smartcop/MIT-Mobile-for-iOS,MIT-Mobile/MIT-Mobile-for-iOS