Fix leak in network analysis director

Author: nyalldawson

python/analysis/network/qgsgraphdirector.sip.in

@@ -32,6 +32,8 @@ using "builder" design patter.
 %End
   public:
 
+    ~QgsGraphDirector();
+
     virtual void makeGraph( QgsGraphBuilderInterface *builder,
                             const QVector< QgsPointXY > &additionalPoints,
                             QVector< QgsPointXY > &snappedPoints /Out/,

src/analysis/network/qgsgraphdirector.h

@@ -56,6 +56,11 @@ class ANALYSIS_EXPORT QgsGraphDirector : public QObject
 
   public:
 
+    ~QgsGraphDirector()
+    {
+      qDeleteAll( mStrategies );
+    }
+
     /**
      * Make a graph using QgsGraphBuilder
      *