properly define PNG_CLEANUP

Should fix https://github.com/google/oss-fuzz/issues/809
diff --git a/contrib/oss-fuzz/libpng_read_fuzzer.cc b/contrib/oss-fuzz/libpng_read_fuzzer.cc
index 9135a03..5003a8a 100644
--- a/contrib/oss-fuzz/libpng_read_fuzzer.cc
+++ b/contrib/oss-fuzz/libpng_read_fuzzer.cc
@@ -87,7 +87,7 @@
     return 0;
   }
 
-#define PNG_CLEANUP
+#define PNG_CLEANUP \
   if(png_handler.png_ptr) \
   { \
     if (png_handler.row_ptr) \
@@ -103,7 +103,7 @@
     png_handler.png_ptr = nullptr; \
     png_handler.row_ptr = nullptr; \
     png_handler.info_ptr = nullptr; \
-    png_handler.end_info_ptr = nullptr;
+    png_handler.end_info_ptr = nullptr; \
   }
 
   png_handler.info_ptr = png_create_info_struct(png_handler.png_ptr);