mpm-hs,spm-hs: don't call hs_scan() for zero bytes

src/util-mpm-hs.c

@@ -919,6 +919,10 @@ uint32_t SCHSSearch(const MpmCtx *mpm_ctx, MpmThreadCtx *mpm_thread_ctx,
     SCHSThreadCtx *hs_thread_ctx = (SCHSThreadCtx *)(mpm_thread_ctx->ctx);
     const PatternDatabase *pd = ctx->pattern_db;
 
+    if (unlikely(buflen == 0)) {
+        return 0;
+    }
+
     SCHSCallbackCtx cctx = {.ctx = ctx, .pmq = pmq, .match_count = 0};
 
     /* scratch should have been cloned from g_scratch_proto at thread init. */

src/util-spm-hs.c

@@ -141,6 +141,10 @@ static uint8_t *HSScan(const SpmCtx *ctx, SpmThreadCtx *thread_ctx,
     const SpmHsCtx *sctx = ctx->ctx;
     hs_scratch_t *scratch = thread_ctx->ctx;
 
+    if (unlikely(haystack_len == 0)) {
+        return NULL;
+    }
+
     uint64_t match_offset = UINT64_MAX;
     hs_error_t err = hs_scan(sctx->db, (const char *)haystack, haystack_len, 0,
                              scratch, MatchEvent, &match_offset);