Fix: InBoundMatching does not properly accept passed-in buffer

[nirmal-vuppuluri]

InBoundMatching() checks whether the length of the passed-in buffer is > 0 and if so, uses it. However, this does not properly handle the case where the passed-in buffer is allocated, i.e. cap(buf) > 0 and len(buf) == 0.

[paulmach]

Thank you