Fix query digests for comments for certain query sizes - Closes #4918.

[JavierJF]

Closes #4918.

This patches has been tested using the AFL++ tests with the following clean results:

[AFL++ 81ffae2edf4f] /src/test/afl_digest_test # afl-whatsup -s output/
/usr/local/bin/afl-whatsup status check tool for afl-fuzz by Michal Zalewski

Summary stats
=============

        Fuzzers alive : 5
          Starting up : 1 (excluded from stats)
       Total run time : 1 days, 6 hours
          Total execs : 1374 millions
     Cumulative speed : 62007 execs/sec
  Total average speed : 12401 execs/sec
Current average speed : 59955 execs/sec
        Pending items : 0 faves, 0 total
   Pending per fuzzer : 0 faves, 0 total (on average)
     Coverage reached : 1.30%
        Crashes saved : 0
          Hangs saved : 0
 Cycles without finds : 37/312/73/76/65
   Time without finds : 28 minutes, 44 seconds