Fix GCC build issue in fxcodec.DecodeDataZeroSize test (try 2)

https://pdfium-review.googlesource.com/131330 didn't actually work.

Change-Id: Id4900b304966e6fdfab46a510f4c7c92d2e1a9dd
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/131750
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxcodec/jpx/jpx_unittest.cpp b/core/fxcodec/jpx/jpx_unittest.cpp
index d84a2c2..f54528a 100644
--- a/core/fxcodec/jpx/jpx_unittest.cpp
+++ b/core/fxcodec/jpx/jpx_unittest.cpp
@@ -71,7 +71,8 @@
 }
 
 TEST(fxcodec, DecodeDataZeroSize) {
-  DecodeData dd(pdfium::span(kStreamData).first(0u));
+  static constexpr pdfium::span<const uint8_t> kEmptySpan;
+  DecodeData dd(kEmptySpan);
   uint8_t buffer[16];
 
   // Reads of size 0 do nothing but return an error code.