[fuzz] Only set HUF_repeat_valid if loaded table has all non-zero weights (#1898)

Fixes a fuzz issue where dictionary_round_trip failed because the compressor was generating corrupt files thanks to zero weights in the table.

* Only setting loaded dict huf table to valid on non-zero

* Adding hasNoZeroWeights test to fse tables

* Forbiding nbBits != 0 when weight == 0

* Reverting the last commit

* Setting table log to 0 when weight == 0

* Small (invalid) zero weight dict test

* Small (valid) zero weight dict test

* Initializing repeatMode vars to check before zero check

* Removing FSE changes to seperate pr

* Reverting accidentally changed file

* Negating bool, using unsigned, optimization nit

tests/playTests.sh

@@ -502,6 +502,22 @@ cmp tmp tmp_decompress || die "difference between original and decompressed file
 println "test : incorrect stream size"
 cat tmp | $ZSTD -14 -f -o tmp.zst --stream-size=11001 && die "should fail with incorrect stream size"
 
+println "\n===>  zstd zero weight dict test "
+rm -f tmp*
+cp "$TESTDIR/dict-files/zero-weight-dict" tmp_input
+$ZSTD -D "$TESTDIR/dict-files/zero-weight-dict" tmp_input
+$ZSTD -D "$TESTDIR/dict-files/zero-weight-dict" -d tmp_input.zst -o tmp_decomp
+$DIFF tmp_decomp tmp_input
+rm -rf tmp*
+
+println "\n===>  zstd (valid) zero weight dict test "
+rm -f tmp*
+# 0 has a non-zero weight in the dictionary
+echo "0000000000000000000000000" > tmp_input
+$ZSTD -D "$TESTDIR/dict-files/zero-weight-dict" tmp_input
+$ZSTD -D "$TESTDIR/dict-files/zero-weight-dict" -d tmp_input.zst -o tmp_decomp
+$DIFF tmp_decomp tmp_input
+rm -rf tmp*
 
 println "\n===>  size-hint mode"
 
@@ -1189,7 +1205,6 @@ $ZSTD --train-cover "$TESTDIR"/*.c "$PRGDIR"/*.c
 test -f dictionary
 rm -f tmp* dictionary
 
-
 if [ "$isWindows" = false ] ; then
 
 println "\n===>  zstd fifo named pipe test "