Warnings when compiling with GCC 13.2

[FitzRoyX]

In file included from ../thirdparty/ymfm/src/ymfm_opl.cpp:32:
../thirdparty/ymfm/src/ymfm_fm.ipp: In member function 'void ymfm::fm_engine_base<RegisterType>::engine_timer_expired(uint32_t) [with RegisterType = ymfm::opl_registers_base<3>]':
../thirdparty/ymfm/src/ymfm_fm.ipp:1523:31: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1523 |         m_timer_running[tnum] = false;
      |         ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
In file included from ../thirdparty/ymfm/src/ymfm_opl.h:38,
                 from ../thirdparty/ymfm/src/ymfm_opl.cpp:31:
../thirdparty/ymfm/src/ymfm_fm.h:448:17: note: at offset 2 into destination object 'ymfm::fm_engine_base<ymfm::opl_registers_base<3> >::m_timer_running' of size 2
  448 |         uint8_t m_timer_running[2];      // current timer running state
      |                 ^~~~~~~~~~~~~~~
Compiling thirdparty/ymfm/src/ymfm_pcm.cpp ...
../thirdparty/ymfm/src/ymfm_fm.ipp: In member function 'void ymfm::fm_engine_base<RegisterType>::engine_timer_expired(uint32_t) [with RegisterType = ymfm::opl_registers_base<4>]':
../thirdparty/ymfm/src/ymfm_fm.ipp:1523:31: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1523 |         m_timer_running[tnum] = false;
      |         ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
../thirdparty/ymfm/src/ymfm_fm.h:448:17: note: at offset 2 into destination object 'ymfm::fm_engine_base<ymfm::opl_registers_base<4> >::m_timer_running' of size 2
  448 |         uint8_t m_timer_running[2];      // current timer running state
      |                 ^~~~~~~~~~~~~~~
In file included from ../thirdparty/ymfm/src/ymfm_opq.cpp:32:
../thirdparty/ymfm/src/ymfm_fm.ipp: In member function 'void ymfm::fm_engine_base<RegisterType>::engine_timer_expired(uint32_t) [with RegisterType = ymfm::opq_registers]':
../thirdparty/ymfm/src/ymfm_fm.ipp:1523:31: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1523 |         m_timer_running[tnum] = false;
      |         ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
In file included from ../thirdparty/ymfm/src/ymfm_opq.h:37,
                 from ../thirdparty/ymfm/src/ymfm_opq.cpp:31:
../thirdparty/ymfm/src/ymfm_fm.h:448:17: note: at offset 2 into destination object 'ymfm::fm_engine_base<ymfm::opq_registers>::m_timer_running' of size 2
  448 |         uint8_t m_timer_running[2];      // current timer running state
      |                 ^~~~~~~~~~~~~~~