When disconnected, connectedState.value.connected is still true.

To repro:
1. Connect devtools to counter app on android emulator
2. Open memory chart (with enabled android chart)
3. Kill the emulator
4. See exception

Code:
```
try {
await _memoryTracker.pollMemory();
} catch (e) {
print('Error polling memory: $e');
if (serviceConnection.serviceManager.connectedState.value.connected) {
rethrow;
}
}
```

Video:

https://github.com/flutter/devtools/assets/12115586/0c6d1904-6f9d-4942-922d-8d0fd89ea6ed