monitor: fix maybe-uninitialized

../monitor/misc.c: In function ‘mon_get_cpu_sync’:
/home/elmarco/src/qq/include/sysemu/hw_accel.h:22:9: error: ‘cpu’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
   22 |         kvm_cpu_synchronize_state(cpu);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../monitor/misc.c:397:15: note: ‘cpu’ was declared here
  397 |     CPUState *cpu;
      |               ^~~

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/monitor/misc.c b/monitor/misc.c
index 3baa15f..a74cff3 100644
--- a/monitor/misc.c
+++ b/monitor/misc.c
@@ -394,7 +394,7 @@
 /* Callers must hold BQL. */
 static CPUState *mon_get_cpu_sync(bool synchronize)
 {
-    CPUState *cpu;
+    CPUState *cpu = NULL;
 
     if (cur_mon->mon_cpu_path) {
         cpu = (CPUState *) object_resolve_path_type(cur_mon->mon_cpu_path,
@@ -411,6 +411,7 @@
         monitor_set_cpu(first_cpu->cpu_index);
         cpu = first_cpu;
     }
+    assert(cpu != NULL);
     if (synchronize) {
         cpu_synchronize_state(cpu);
     }