Raise proper error when decoding 16-bits jpegs (#4101)

Author: cyyever

torchvision/csrc/io/image/cpu/decode_png.cpp

@@ -71,6 +71,11 @@ torch::Tensor decode_png(const torch::Tensor& data, ImageReadMode mode) {
     TORCH_CHECK(retval == 1, "Could read image metadata from content.")
   }
 
+  if (bit_depth > 8) {
+    png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
+    TORCH_CHECK(false, "At most 8-bit PNG images are supported currently.")
+  }
+
   int channels = png_get_channels(png_ptr, info_ptr);
 
   if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)