fix compare_MapNode_

why does this need to be specified manually?

src/media.c

@@ -196,7 +196,7 @@ void delete_StatefulJxlDecoder(iStatefulJxlDecoder *s) {
 }
 
 static int compare_MapNode_(iMapKey a, iMapKey b) {
-    return a < b;
+    return (a > b) - (a < b);
 }
 
 static uint8_t *loadJxl_(const iBlock *data, iInt2 *imSize, iGmLinkId linkId, iBool isPartial) {