Add missing makeCurrent()

Alpha_shapes_3/demo/Alpha_shapes_3/Viewer.h

@@ -21,6 +21,7 @@ public:
   Viewer(QWidget* parent);
   ~Viewer()
   {
+    makeCurrent();
     buffers[0].destroy();
     buffers[1].destroy();
     buffers[2].destroy();

Circular_kernel_3/demo/Circular_kernel_3/Viewer.cpp

@@ -11,6 +11,14 @@ Viewer::Viewer(QWidget* parent )
 {
     extension_is_found = false;
 }
+Viewer::~Viewer()
+{
+  makeCurrent();
+  for(int i=0; i<3; ++i)
+    vao[i].destroy();
+  for(int i=0; i<9; ++i)
+    buffers[i].destroy();
+}
 
 void Viewer::compile_shaders()
 {

Circular_kernel_3/demo/Circular_kernel_3/Viewer.h

@@ -13,6 +13,7 @@ class Viewer : public CGAL::QGLViewer
 {
 public:
     Viewer(QWidget* parent = 0);
+    ~Viewer();
   GLuint dl_nb;
 protected :
   virtual void draw();

Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/Scene.h

@@ -76,6 +76,7 @@ public:
   }
 
   ~Scene() {
+    ui->viewer->makeCurrent();
     for(int i=0; i<24; i++)
         buffers[i].destroy();
     for(int i=0; i<12; i++)

Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/Viewer.h

@@ -27,6 +27,7 @@ public:
   {}
   ~Viewer()
   {
+    makeCurrent();
    for(int i=0; i<4; i++)
    {
     buffers[i].destroy();

Polyhedron/demo/Polyhedron/Viewer.cpp

@@ -374,6 +374,7 @@ Viewer::Viewer(QWidget* parent,
 
 Viewer::~Viewer()
 {
+  makeCurrent();
     QSettings viewer_settings;
     viewer_settings.setValue("cam_pos",
                              QString("%1,%2,%3")