common: add an extra check in autobuf_enlarge to avoid a compiler warning
common: add an extra check in autobuf_enlarge to avoid a compiler warning

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

diogomg/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd,tdz/olsrd,sebkur/olsrd,diogomg/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd,cholin/olsrd,nolith/olsrd,tdz/olsrd,cholin/olsrd,cholin/olsrd,sebkur/olsrd,diogomg/olsrd,sebkur/olsrd,nolith/olsrd,cholin/olsrd,tdz/olsrd,diogomg/olsrd,cholin/olsrd,nolith/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd-binary-heap,nolith/olsrd,sebkur/olsrd,diogomg/olsrd,diogomg/olsrd-binary-heap,tdz/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,tdz/olsrd,nolith/olsrd