refactor: Restore previous OpenScreenEvent#getNewScreen quirk to avoid semantic breaking change

Author: BlayTheNinth

common/src/main/java/net/blay09/mods/balm/api/event/client/OpenScreenEvent.java

@@ -22,6 +22,6 @@ public void setScreen(@Nullable Screen screen) {
     }
 
     public @Nullable Screen getNewScreen() {
-        return newScreen;
+        return newScreen != screen ? newScreen : null;
     }
 }