mdns: fix uninitialised pointer for first nonOlsrInterface
mdns: fix uninitialised pointer for first nonOlsrInterface

just like in 1b8be499965fdeea0b3bdd1dbfb610bceea8928f

Signed-off-by: Ferry Huberts <66e11f9f5d965b69497c7e73d5e808f8b13c1218@pelagic.nl>

servalproject/olsr,nolith/olsrd,tdz/olsrd,sebkur/olsrd,diogomg/olsrd-binary-heap,nolith/olsrd,ninuxorg/olsrd,brabander/olsr,diogomg/olsrd-binary-heap,zioproto/olsrd,duydb2/olsr,duydb2/olsr,diogomg/olsrd,acinonyx/olsrd,sebkur/olsrd,nolith/olsrd,servalproject/olsr,sebkur/olsrd,cholin/olsrd,duydb2/olsr,diogomg/olsrd-binary-heap,servalproject/olsr,acinonyx/olsrd,sebkur/olsrd,servalproject/olsr,sebkur/olsrd,zioproto/olsrd,nolith/olsrd,servalproject/olsr,brabander/olsr,duydb2/olsr,acinonyx/olsrd,ninuxorg/olsrd,tdz/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd,duydb2/olsr,cholin/olsrd,brabander/olsr,duydb2/olsr,tdz/olsrd,nolith/olsrd,diogomg/olsrd-binary-heap,acinonyx/olsrd,zioproto/olsrd,tdz/olsrd,diogomg/olsrd,ninuxorg/olsrd,cholin/olsrd,diogomg/olsrd,servalproject/olsr,duydb2/olsr,cholin/olsrd,diogomg/olsrd,tdz/olsrd,cholin/olsrd,duydb2/olsr,brabander/olsr,diogomg/olsrd-binary-heap,acinonyx/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd,ninuxorg/olsrd,diogomg/olsrd,zioproto/olsrd,zioproto/olsrd,ninuxorg/olsrd