In 89ba00304c, the box' X position was
capped at 0 to prevent negative X positions to act as if there were
intruding floats on the left side. Instead, we need to check whether the
left side float intrusion we are going to calculate matters at all -
because if there's no matching float box, the intrusion is always going
to be 0 and we don't need to take the box' X position into account.
Fixes the floating publication images on https://lexfridman.com/.
