Another nullptr-arithmetics clamer

PiperOrigin-RevId: 721727118

c/enc/block_splitter_inc.h

diff --git a/c/enc/block_splitter_inc.h b/c/enc/block_splitter_inc.h
index 64409ec..f7c4345 100644
--- a/c/enc/block_splitter_inc.h
+++ b/c/enc/block_splitter_inc.h
@@ -230,12 +230,16 @@
   static const uint32_t kInvalidIndex = BROTLI_UINT32_MAX;
   uint32_t* new_index;
   size_t i;
-  uint32_t* BROTLI_RESTRICT const sizes = u32 + 0 * HISTOGRAMS_PER_BATCH;
-  uint32_t* BROTLI_RESTRICT const new_clusters = u32 + 1 * HISTOGRAMS_PER_BATCH;
-  uint32_t* BROTLI_RESTRICT const symbols = u32 + 2 * HISTOGRAMS_PER_BATCH;
-  uint32_t* BROTLI_RESTRICT const remap = u32 + 3 * HISTOGRAMS_PER_BATCH;
+  uint32_t* BROTLI_RESTRICT const sizes =
+      u32 ? (u32 + 0 * HISTOGRAMS_PER_BATCH) : NULL;
+  uint32_t* BROTLI_RESTRICT const new_clusters =
+      u32 ? (u32 + 1 * HISTOGRAMS_PER_BATCH) : NULL;
+  uint32_t* BROTLI_RESTRICT const symbols =
+      u32 ? (u32 + 2 * HISTOGRAMS_PER_BATCH) : NULL;
+  uint32_t* BROTLI_RESTRICT const remap =
+      u32 ? (u32 + 3 * HISTOGRAMS_PER_BATCH) : NULL;
   uint32_t* BROTLI_RESTRICT const block_lengths =
-      u32 + 4 * HISTOGRAMS_PER_BATCH;
+      u32 ? (u32 + 4 * HISTOGRAMS_PER_BATCH) : NULL;
   /* TODO(eustas): move to arena? */
   HistogramType* tmp = BROTLI_ALLOC(m, HistogramType, 2);