[wasm] Fix decoder for null data

test/unittests/wasm/decoder-unittest.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/unittests/test-utils.h"
 
 #include "src/objects-inl.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/wasm-macro-gen.h"
 
@@ skipping 653 matching lines @@
 TEST_F(DecoderTest, ReadI64v_extra_bits_positive) {
   // Not OK for positive signed values to have extra ones.
   unsigned length = 0;
   byte data[] = {0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x77};
   decoder.Reset(data, data + sizeof(data));
   decoder.checked_read_i64v(decoder.start(), 0, &length);
   EXPECT_EQ(10, length);
   EXPECT_FALSE(decoder.ok());
 }
 
+TEST_F(DecoderTest, FailOnNullData) {
+  decoder.Reset(nullptr, 0);
+  decoder.checkAvailable(1);
+  EXPECT_FALSE(decoder.ok());
+  EXPECT_FALSE(decoder.toResult(nullptr).ok());
+}
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8