[Bug] rt_thread_kill 多次执行触发 ASSERT

[rcitach]

RT-Thread Version

5.2.2

Hardware Type/Architectures

RK3500

Develop Toolchain

GCC

Describe the bug

在 rt-thread/examples/utest/testcases/kernel/signal_tc.c 测试代码运行过程中发现，多次执行会触发 block_ptr 为空的错误：

跟踪发现 rt_thread_kill 中会一直执行 rt_mp_alloc ，导致资源耗尽

Other additional context

No response