TerminalWidget: Fix a warning about no return value

Amends a0c05cabcc

Change-Id: Ieb969f7a6c61469f69e8503089e4985fa8380e3c
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/plugins/terminal/terminalwidget.cpp

@@ -635,6 +635,7 @@ void TerminalWidget::initActions(QObject *parent)
             return {QKeySequence(QLatin1String("Ctrl+") + key),
                     QKeySequence(QLatin1String("Ctrl+Shift+") + key)};
         }
+        return {};
     };
 
     ActionBuilder copyAction(parent, Constants::COPY);