lq: make sure last_ip != NULL
lq: make sure last_ip != NULL

Coverity:
CID 739653 (#1 of 1): Explicit null dereferenced (FORWARD_NULL)
At (11): Passing null pointer "last_ip" to function
         "calculate_border_flag(void *, void *)", which dereferences it.

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

diogomg/olsrd,ninuxorg/olsrd,cholin/olsrd,zioproto/olsrd,sebkur/olsrd,tdz/olsrd,acinonyx/olsrd,nolith/olsrd,zioproto/olsrd,sebkur/olsrd,diogomg/olsrd,tdz/olsrd,sebkur/olsrd,diogomg/olsrd-binary-heap,ninuxorg/olsrd,ninuxorg/olsrd,acinonyx/olsrd,cholin/olsrd,diogomg/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,nolith/olsrd,acinonyx/olsrd,cholin/olsrd,sebkur/olsrd,zioproto/olsrd,acinonyx/olsrd,zioproto/olsrd,nolith/olsrd,diogomg/olsrd,zioproto/olsrd,sebkur/olsrd,diogomg/olsrd,ninuxorg/olsrd,tdz/olsrd,diogomg/olsrd,cholin/olsrd,diogomg/olsrd,acinonyx/olsrd,nolith/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,nolith/olsrd,diogomg/olsrd-binary-heap,ninuxorg/olsrd,cholin/olsrd,diogomg/olsrd-binary-heap,tdz/olsrd,diogomg/olsrd-binary-heap,tdz/olsrd