bug in NormalizeCount()

[richgel999]

Hi,

freqs[argmax] can be decremented below zero, causing encoding to fail. Here's one way to fix that:

 // A symbol must have freq at least 1
        for (int i = 0; i < num_symbols; i++) {
            if (freqs[i] == 0) {
                freqs[i] = 1;
                
                freqs[argmax]--;

                assert(freqs[argmax] >= 1);
                
                argmax = (int)std::distance(freqs.begin(), std::max_element(freqs.begin(), freqs.end()));
            }
        }