TreeViewFind: Fix endless loop if tree view has nothing selected

If the tree view has nothing selected, the search would wrap endlessly
because the current index is invalid, but wrapping restarted at the
first toplevel index.

Change-Id: I31badb2038c8752d2c91e6fcaff69138c846383e
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/coreplugin/find/treeviewfind.cpp

@@ -157,10 +157,14 @@ IFindSupport::Result TreeViewFind::find(const QString &searchTxt,
         *wrapped = false;
     if (searchTxt.isEmpty())
         return IFindSupport::NotFound;
+    if (d->m_view->model()->rowCount() <= 0) // empty model
+        return IFindSupport::NotFound;
 
+    QModelIndex currentIndex = d->m_view->currentIndex();
+    if (!currentIndex.isValid()) // nothing selected, start from top
+        currentIndex = d->m_view->model()->index(0, 0);
     QTextDocument::FindFlags flags = textDocumentFlagsForFindFlags(findFlags);
     QModelIndex resultIndex;
-    QModelIndex currentIndex = d->m_view->currentIndex();
     QModelIndex index = currentIndex;
     int currentRow = currentIndex.row();