fix non-constant init

Reference: /n/atom/patch/applied/sokofix
Date: Sun Aug 16 05:47:50 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/games/sokoban/sokoban.c	Sun Aug 16 05:47:41 2015
+++ /sys/src/games/sokoban/sokoban.c	Sun Aug 16 05:47:42 2015
@@ -41,7 +41,7 @@
 
 Menu lmenu =
 {
-	levelnames,
+	nil,
 };
 
 void