Fix potential memory leak.

Author: bokic

analysis/lengthdistributionanalysis.cpp

@@ -29,11 +29,11 @@ QWidget *LengthDistributionAnalysis::createResultWidget()
     QChartView * view = new QChartView;
     view->setRenderHint(QPainter::Antialiasing);
 
-    QLineSeries * serie = new QLineSeries;
-
     if (mGraphCounts.isEmpty())
         return view;
 
+    QLineSeries * serie = new QLineSeries;
+
     int yMax = 0;
     auto graph_count_it = mGraphCounts.begin();
     for (int i=mMin; i < mMax+mIntervale; i += mIntervale)