RegEx() 在大量快速调用时有概率出现错误

[zhenzh]

重现方法：
for i=1,100000 do Print(tostring(i)..": "..RegEx("test", "(^.*$)")) end

Lua error: :1: bad argument #1 to ? (string expected, got nil)
stack traceback:
:0: in function </Users/ibm/go-mud/script/frame/timer.lua:5>
:1: in function <:0>
/Users/ibm/go-mud/script/client.lua:182: in main chunk