Fix silly assert in world-core

luprex/core/cpp/world-core.cpp

@@ -725,7 +725,9 @@ void World::guard_nopredict(lua_State *L, const char *fn) {
 }
 
 void World::schedule(int64_t clk, int64_t thid, int64_t plid) {
-    assert(is_authoritative());
+    if (clk > 0) {
+        assert(is_authoritative());
+    }
     thread_sched_.add(clk, thid, plid);
 }