Replace 0 pointer with NULL in docs (fixes #610) (#713)
Replace 0 pointer with NULL in docs (fixes #610) (#713)


libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl