Fix a *fu***** bug in reverse package merge algorithm.
Fix a *fu***** bug in reverse package merge algorithm.

This algorithm fails when all frequencies equal 0. In this case
(generally with distance frequencies in random string), the program
raise [index of bound]. But, in Zlib, we add 2 dummy frequencies to
create a minimal huffman tree - so this patch do this.

oklm-wsh/Decompress,oklm-wsh/Decompress