[ VM / Service ] Initialize ThreadInterrupter state even if profiler isn't enabled.

Fixes issue #36586.

Change-Id: I2e3807d00d10e262201295744b6da8249a337e19
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99344
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Jacob Richman <jacobr@google.com>

runtime/vm/thread_interrupter.cc

@@ -116,6 +116,10 @@ void ThreadInterrupter::Cleanup() {
 
 // Delay between interrupts.
 void ThreadInterrupter::SetInterruptPeriod(intptr_t period) {
+  if (!initialized_) {
+    // Profiler may not be enabled.
+    return;
+  }
   MonitorLocker ml(monitor_);
   if (shutdown_) {
     return;