assert removed in 'luaO_arith'

(nobody calls it with L==NULL)

lobject.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.c,v 2.113 2016/12/22 13:08:50 roberto Exp roberto $
+** $Id: lobject.c,v 2.114 2017/04/19 16:34:35 roberto Exp roberto $
 ** Some generic functions over Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -155,7 +155,6 @@ void luaO_arith (lua_State *L, int op, const TValue *p1, const TValue *p2,
     }
   }
   /* could not perform raw operation; try metamethod */
-  lua_assert(L != NULL);  /* should not fail when folding (compile time) */
   luaT_trybinTM(L, p1, p2, res, cast(TMS, (op - LUA_OPADD) + TM_ADD));
 }