Fix build failure.

fuzz/fuzz-read-print-write.cpp

@@ -17,7 +17,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size) {
   try {
     Exiv2::DataBuf data_copy(data, size);
     Exiv2::Image::UniquePtr image =
-      Exiv2::ImageFactory::open(data_copy.pData_, size);
+      Exiv2::ImageFactory::open(data_copy.c_data(0), size);
     assert(image.get() != 0);
 
     image->readMetadata();