Debugger: Don't fetch more data for console after engine shutdown

The engine might not exist anymore.

Change-Id: I7a542de7fb8b160d71a1650d37263e4433f97003
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/console/console.cpp

@@ -249,6 +249,7 @@ void Console::writeSettings() const
 void Console::setScriptEvaluator(const ScriptEvaluator &evaluator)
 {
     m_scriptEvaluator = evaluator;
+    m_consoleItemModel->setCanFetchMore(bool(m_scriptEvaluator));
     if (!m_scriptEvaluator)
         setContext(QString());
 }