Fix memory leak in QJsonModel.

src/libcalamaresui/utils/qjsonmodel.cpp

@@ -36,6 +36,13 @@ QJsonModel::QJsonModel(QObject *parent) :
 
 }
 
+
+QJsonModel::~QJsonModel()
+{
+    delete mRootItem;
+}
+
+
 bool QJsonModel::load(const QString &fileName)
 {
     QFile file(fileName);

src/libcalamaresui/utils/qjsonmodel.h

@@ -31,6 +31,7 @@ class QJsonModel : public QAbstractItemModel
     Q_OBJECT
 public:
     explicit QJsonModel(QObject *parent = 0);
+    virtual ~QJsonModel();
     bool load(const QString& fileName);
     bool load(QIODevice * device);
     bool loadJson(const QByteArray& json);