[libpng16] Revise contrib/oss-fuzz/libpng_read_fuzzer.cc
diff --git a/contrib/oss-fuzz/libpng_read_fuzzer.cc b/contrib/oss-fuzz/libpng_read_fuzzer.cc
index dd23563..2e8229d 100644
--- a/contrib/oss-fuzz/libpng_read_fuzzer.cc
+++ b/contrib/oss-fuzz/libpng_read_fuzzer.cc
@@ -5,7 +5,7 @@
 // Use of this source code is governed by a BSD-style license that may
 // be found in the LICENSE file https://cs.chromium.org/chromium/src/LICENSE
 
-// Last changed in libpng 1.6.33beta02 [September 3, 2017]
+// Last changed in libpng 1.6.33beta02 [September 4, 2017]
 
 // The modifications in 2017 by Glenn Randers-Pehrson include
 // 1. addition of a PNG_CLEANUP macro,
@@ -36,14 +36,12 @@
   BufState* buf_state = nullptr;
 
   ~PngObjectHandler() {
-    if (png_handler.row_ptr)
-      png_free(png_handler.png_ptr, png_handler.row_ptr);
-    if (png_handler.end_info_ptr)
-      png_destroy_read_struct(&png_handler.png_ptr, &png_handler.info_ptr,
-        &png_handler.end_info_ptr);
-    else if (png_handler.info_ptr) 
-      png_destroy_read_struct(&png_handler.png_ptr, &png_handler.info_ptr,
-        nullptr);
+    if (row_ptr)
+      png_free(png_ptr, row_ptr);
+    if (end_info_ptr)
+      png_destroy_read_struct(&png_ptr, &info_ptr, &end_info_ptr);
+    else if (info_ptr) 
+      png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
     else
       png_destroy_read_struct(&png_handler.png_ptr, nullptr, nullptr);
     delete buf_state;