Git: Fix soft assertion

First selectionChanged when dialog is opened always has empty index for
previous.

Change-Id: I024374f9e61fffae351f15af54f769ddf84ded75
Reviewed-by: Petar Perisin <petar.perisin@gmail.com>

src/plugins/git/logchangedialog.cpp

@@ -130,7 +130,8 @@ void LogChangeWidget::selectionChanged(const QItemSelection &selected,
     if (!m_hasCustomDelegate)
         return;
     const QModelIndexList previousIndexes = deselected.indexes();
-    QTC_ASSERT(!previousIndexes.isEmpty(), return);
+    if (previousIndexes.isEmpty())
+        return;
     const QModelIndex current = currentIndex();
     int row = current.row();
     int previousRow = previousIndexes.first().row();