Fix sorting of indexed palettes

Author: Rangi42

src/gfx/pal_sorting.cpp

@@ -24,10 +24,11 @@ void sortIndexed(
 		);
 	};
 
-	for (Palette &pal : palettes) {
+	for (size_t palID = 0; palID < palettes.size(); ++palID) {
+		Palette &pal = palettes[palID];
 		std::sort(RANGE(pal), [&](uint16_t lhs, uint16_t rhs) {
 			// Iterate through the PNG's palette, looking for either of the two
-			for (int i = 0; i < palSize; ++i) {
+			for (size_t i = palID * 4; i < palID * 4 + 4; ++i) {
 				uint16_t color = pngToRgb(i).cgbColor();
 				if (color == Rgba::transparent) {
 					continue;