KExtraColumnsProxyModel: implement buddy() to fix runtime warning.

autotests/kextracolumnsproxymodeltest.cpp

@@ -175,6 +175,9 @@ private Q_SLOTS:
         QCOMPARE(pm.index(0, 0).sibling(0, 4).column(), 4);
         QCOMPARE(pm.index(0, 4).sibling(0, 1).column(), 1);
 
+        QCOMPARE(pm.buddy(pm.index(0, 0)), pm.index(0, 0));
+        QCOMPARE(pm.buddy(pm.index(0, 4)), pm.index(0, 4));
+
         QVERIFY(!pm.canFetchMore(QModelIndex()));
     }
 

src/kextracolumnsproxymodel.cpp

@@ -121,6 +121,15 @@ QModelIndex KExtraColumnsProxyModel::mapToSource(const QModelIndex &proxyIndex)
     return QIdentityProxyModel::mapToSource(proxyIndex);
 }
 
+QModelIndex KExtraColumnsProxyModel::buddy(const QModelIndex &proxyIndex) const
+{
+    const int column = proxyIndex.column();
+    if (column >= sourceModel()->columnCount()) {
+        return proxyIndex;
+    }
+    return QIdentityProxyModel::buddy(proxyIndex);
+}
+
 QModelIndex KExtraColumnsProxyModel::sibling(int row, int column, const QModelIndex &idx) const
 {
     if (row == idx.row() && column == idx.column()) {

src/kextracolumnsproxymodel.h

@@ -133,6 +133,8 @@ public:
     /// @reimp
     QModelIndex sibling(int row, int column, const QModelIndex &idx) const Q_DECL_OVERRIDE;
     /// @reimp
+    QModelIndex buddy(const QModelIndex &index) const Q_DECL_OVERRIDE;
+    /// @reimp
     Qt::ItemFlags flags(const QModelIndex &index) const Q_DECL_OVERRIDE;
     /// @reimp
     QVariant headerData(int section, Qt::Orientation orientation,