fixed armarx plotter: plotter could crash when now data was available

source/RobotAPI/gui-plugins/SensorActorWidgetsPlugin/ArmarXPlotter/ArmarXPlotter.cpp

@@ -390,7 +390,7 @@ namespace armarx
 
             QwtSeriesData<QPointF>* pointSeries = new  QwtPointSeriesData(pointList);
 
-            if (curves.find(it->first) != curves.end() && bars.find(it->first) != bars.end())
+            if (pointList.size() > 0 && curves.find(it->first) != curves.end() && bars.find(it->first) != bars.end())
             {
                 QwtPlotCurve* curve = curves[it->first];
                 curve->setData(pointSeries);
@@ -686,7 +686,7 @@ namespace armarx
                 //            QDateTime time(QDateTime::currentDateTime());
                 TimedVariantBaseList variants = proxyMap[observerName]->getDataFields(it->second);
 
-                //                ARMARX_IMPORTANT << "data from observer: " << observerName;
+                //            #    ARMARX_IMPORTANT << "data from observer: " << observerName;
                 for (unsigned int i = 0; i < variants.size(); ++i)
                 {
                     //                    ARMARX_IMPORTANT << "Variant: " << VariantPtr::dynamicCast(variants[i]);