Kernel: Fix LOCK_DEBUG feature to work again

- UBSAN detected cases where we were calling thread->holding_lock(..)
  but current_thread was nullptr.

- Fix Lock::force_unlock_if_locked to not pass the correct ref delta to
  holding_lock(..).

Kernel/Lock.cpp

@@ -53,7 +53,9 @@ void Lock::lock(Mode mode)
  VERIFY(m_times_locked == 0);
  m_times_locked++;
 #if LOCK_DEBUG
- current_thread->holding_lock(*this, 1, file, line);
+ if (current_thread) {
+ current_thread->holding_lock(*this, 1, file, line);
+ }
 #endif
  m_queue.should_block(true);
  m_lock.store(false, AK::memory_order_release);
@@ -165,7 +167,9 @@ void Lock::unlock()
  }
 
 #if LOCK_DEBUG
- current_thread->holding_lock(*this, -1);
+ if (current_thread) {
+ current_thread->holding_lock(*this, -1);
+ }
 #endif
 
  m_lock.store(false, AK::memory_order_release);
@@ -201,7 +205,7 @@ auto Lock::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
 
  dbgln_if(LOCK_RESTORE_DEBUG, "Lock::force_unlock_if_locked @ {}: unlocking exclusive with lock count: {}", this, m_times_locked);
 #if LOCK_DEBUG
- m_holder->holding_lock(*this, -(int)lock_count_to_restore);
+ m_holder->holding_lock(*this, -(int)m_times_locked);
 #endif
  m_holder = nullptr;
  VERIFY(m_times_locked > 0);