Display "Waiting for data" properly

Display "Waiting for data" instead of "No differences" when creating new
instance of an editor for the same document (e.g. by splitting the view)
during document reload.

Change-Id: If254006de3914ad4416c7405874e8cbea57ddd8d
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/diffeditor/diffeditor.cpp

@@ -663,10 +663,6 @@ void DiffEditor::setupView(IDiffView *view)
 
     view->setDocument(m_document.data());
     view->setSync(m_sync);
-
-    view->beginOperation();
-    view->setDiff(m_document->diffFiles(), m_document->baseDirectory());
-    view->endOperation(true);
     view->setCurrentDiffFileIndex(m_currentDiffFileIndex);
 
     m_stackedWidget->setCurrentWidget(view->widget());