RunControl: Add assert when device is nullptr

Amends cf8d108773

Change-Id: Ic9d947fb038e3e063cb7c2a6c740829252bf4cc7
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/runcontrol.cpp

@@ -596,6 +596,8 @@ void RunControlPrivate::startPortsGathererIfNeededAndContinueStart()
         return;
     }
 
+    QTC_ASSERT(device, continueStart(); return);
+
     const Storage<PortsOutputData> portsStorage;
 
     const auto onDone = [this, portsStorage] {