ChildProcessCoordinator: Fix an issue with a missing ping thread

Following commit 093dbc7df1 pings of a
child process connection need to initialised explicitly. This commit
adds a missing initialisation.

modules/juce_events/interprocess/juce_ConnectedChildProcess.cpp

@@ -169,6 +169,7 @@ bool ChildProcessCoordinator::launchWorkerProcess (const File& executable, const
 
         if (connection->isConnected())
         {
+            connection->startPinging();
             sendMessageToWorker ({ startMessage, specialMessageSize });
             return true;
         }