运行system函数出现崩溃

*Describe the bug
当我运行arm架构程序，在程序执行到system函数的时候出现了崩溃，这好像是子进程的问题，有办法解决吗

[x] Syscall ERROR: ql_syscall_clone DEBUG: 'NoneType' object has no attribute 'cur_thread' Traceback (most recent call last): File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/posix/posix.py", line 374, in load_syscall retval = syscall_hook(self.ql, *params) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/posix/syscall/sched.py", line 46, in ql_syscall_clone f_th = ql.os.thread_management.cur_thread AttributeError: 'NoneType' object has no attribute 'cur_thread' Traceback (most recent call last): File "./qilingstart.py", line 79, in <module> ql.run() File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/core.py", line 595, in run self.os.run() File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/linux/linux.py", line 184, in run self.ql.emu_start(self.ql.loader.elf_entry, self.exit_point, self.ql.timeout, self.ql.count) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/core.py", line 775, in emu_start raise self.internal_exception File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/core_hooks.py", line 127, in wrapper return callback(*args, **kwargs) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/core_hooks.py", line 170, in _hook_intr_cb ret = hook.call(ql, intno) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/core_hooks_types.py", line 25, in call return self.callback(ql, *args) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/linux/linux.py", line 138, in hook_syscall return self.load_syscall() File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/posix/posix.py", line 392, in load_syscall raise e File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/posix/posix.py", line 374, in load_syscall retval = syscall_hook(self.ql, *params) File "/home/tower/miniconda3/envs/iot/lib/python3.8/site-packages/qiling/os/posix/syscall/sched.py", line 46, in ql_syscall_clone f_th = ql.os.thread_management.cur_thread AttributeError: 'NoneType' object has no attribute 'cur_thread'

Reproduce the ARM program's system call failure, then start in qiling/os/posix/syscall/sched.py at ql_syscall_clone and trace how ql.os.thread_management is initialized during ql.run(). Check the POSIX and Linux run paths mentioned in the traceback. Done means system() no longer raises the NoneType cur_thread error for this case.