Fix a crash due to max symbol in a tree >= alphabet size

(cherry picked from commit 15253f91567ce7a2a4a3de8d70e54ba4b0641af3)

Change-Id: I4fbeaea4c712dae3bef078aef9d302b44bc39ffb

src/dec/vp8l.c

@@ -248,6 +248,10 @@ static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
       int i;
       for (i = 0; i < num_symbols; ++i) {
         symbols[i] = VP8LReadBits(br, num_bits);
+        if (symbols[i] >= alphabet_size) {
+          dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
+          return 0;
+        }
         codes[i] = i;
         code_lengths[i] = num_symbols - 1;
       }