Output pane: Fix that height setting could reset

When opening Qt Creator, and closing it without showing an output pane,
it would write a height of 0 into the settings.

Task-number: QTCREATORBUG-16829
Change-Id: Ia8ab0cea6620c4e654060f92f51bd5f0ce10e6b9
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/coreplugin/outputpane.cpp

@@ -183,6 +183,8 @@ void OutputPanePlaceHolder::ensureSizeHintAsMinimum()
 
 int OutputPanePlaceHolder::nonMaximizedSize() const
 {
+    if (!d->m_initialized)
+        return Internal::OutputPaneManager::outputPaneHeightSetting();
     return d->m_nonMaximizedSize;
 }