Fixed crash upon saving a pen stroke with an uninitialized strokesGroup

src/adaptors/UBSvgSubsetAdaptor.cpp

@@ -1116,8 +1116,9 @@ bool UBSvgSubsetAdaptor::UBSvgSubsetWriter::persistScene(int pageIndex)
                 {
                     QColor colorOnDarkBackground = polygonItem->colorOnDarkBackground();
                     QColor colorOnLightBackground = polygonItem->colorOnLightBackground();
+                    UBGraphicsStrokesGroup * sg = polygonItem->strokesGroup();
 
-                    if (colorOnDarkBackground.isValid() && colorOnLightBackground.isValid())
+                    if (colorOnDarkBackground.isValid() && colorOnLightBackground.isValid() && sg)
                     {
                         mXmlWriter.writeAttribute(UBSettings::uniboardDocumentNamespaceUri, "z-value"
                                                   , QString("%1").arg(polygonItem->strokesGroup()->zValue()));
@@ -1126,6 +1127,7 @@ bool UBSvgSubsetAdaptor::UBSvgSubsetWriter::persistScene(int pageIndex)
                                                   , "fill-on-dark-background", colorOnDarkBackground.name());
                         mXmlWriter.writeAttribute(UBSettings::uniboardDocumentNamespaceUri
                                                   , "fill-on-light-background", colorOnLightBackground.name());
+                        qDebug() << "Attributes written";
 
                         groupHoldsInfo = true;
                     }

src/domain/UBGraphicsPolygonItem.cpp

@@ -40,6 +40,7 @@ UBGraphicsPolygonItem::UBGraphicsPolygonItem (QGraphicsItem * parent)
     , mOriginalWidth(-1)
     , mIsNominalLine(false)
     , mStroke(0)
+    , mpGroup(NULL)
 {
     // NOOP
     initialize();
@@ -64,6 +65,7 @@ UBGraphicsPolygonItem::UBGraphicsPolygonItem (const QLineF& pLine, qreal pWidth)
     , mOriginalWidth(pWidth)
     , mIsNominalLine(true)
     , mStroke(0)
+    , mpGroup(NULL)
 {
     // NOOP
     initialize();
@@ -75,6 +77,7 @@ UBGraphicsPolygonItem::UBGraphicsPolygonItem (const QLineF& pLine, qreal pStartW
     , mOriginalWidth(pEndWidth)
     , mIsNominalLine(true)
     , mStroke(0)
+    , mpGroup(NULL)
 {
     // NOOP
     initialize();