Merge "VP8BitReaderSetBuffer: move NULL check to call site" into main

src/dec/idec_dec.c

@@ -141,9 +141,15 @@ static void DoRemap(WebPIDecoder* const idec, ptrdiff_t offset) {
       }
       {
         const uint8_t* const last_start = dec->parts[last_part].buf;
+        // 'last_start' will be NULL when 'idec->state' is < STATE_VP8_PARTS0
+        // and through a portion of that state (when there isn't enough data to
+        // parse the partitions). The bitreader is only used meaningfully when
+        // there is enough data to begin parsing partition 0.
+        if (last_start != NULL) {
           VP8BitReaderSetBuffer(&dec->parts[last_part], last_start,
                                 mem->buf + mem->end - last_start);
         }
+      }
       if (NeedCompressedAlpha(idec)) {
         ALPHDecoder* const alph_dec = dec->alph_dec;
         dec->alpha_data += offset;

src/utils/bit_reader_utils.c

@@ -31,13 +31,12 @@
 void VP8BitReaderSetBuffer(VP8BitReader* const br,
                            const uint8_t* const start,
                            size_t size) {
-  if (start != NULL) {
+  assert(start != NULL);
   br->buf = start;
   br->buf_end = start + size;
   br->buf_max =
       (size >= sizeof(lbit_t)) ? start + size - sizeof(lbit_t) + 1 : start;
 }
-}
 
 void VP8InitBitReader(VP8BitReader* const br,
                       const uint8_t* const start, size_t size) {