Check if the IE is memory allocated to deal with presence/absence of this information
element in Bearer Context Modification Request and add encoding/decoding
in the code.
Note that for decoding the integrity settings may be absent, in which
case we consider NIA0 to be used (no integrity protection). To be refined
if needed.
And for encoding, we always encode integrity settings, even if it's NIA0.
May also be refined if needed.