Use a constant for 0x8001 (#1596)

src/gfx/pal_sorting.cpp

@@ -46,7 +46,7 @@ void sortIndexed(
 }
 
 void sortGrayscale(
-    std::vector<Palette> &palettes, std::array<std::optional<Rgba>, 0x8001> const &colors
+    std::vector<Palette> &palettes, std::array<std::optional<Rgba>, NB_COLOR_SLOTS> const &colors
 ) {
 	options.verbosePrint(Options::VERB_LOG_ACT, "Sorting palette by grayscale bins...\n");
 

src/gfx/process.cpp

@@ -26,8 +26,7 @@
 #include "gfx/proto_palette.hpp"
 
 class ImagePalette {
-	// Use as many slots as there are CGB colors (plus transparency)
-	std::array<std::optional<Rgba>, 0x8001> _colors;
+	std::array<std::optional<Rgba>, NB_COLOR_SLOTS> _colors;
 
 public:
 	ImagePalette() = default;