Notify GUI when batch starts

Closes #4906

rtgui/batchqueue.cc

@@ -597,6 +597,8 @@ void BatchQueue::startProcessing ()
             // start batch processing
             rtengine::startBatchProcessing (next->job, this);
             queue_draw ();
+
+            notifyListener();
         }
     }
 }

rtgui/batchqueuepanel.cc

@@ -281,9 +281,6 @@ void BatchQueuePanel::startBatchProc ()
         // callback in response to the *reported* state.
         queueShouldRun = true;
 
-        // Don't need an update callback from the queue to know it is started:
-        setGuiFromBatchState(true, batchQueue->getEntries().size());
-
         saveOptions();
         batchQueue->startProcessing ();
     }