Avoid warning on empty expressions

For some reason, Q_UNUSED includes already a semicolon, adding one
on the user side creates an additional empty statement.

Change-Id: I9c5e8fac381345a60792cb75e2938fd53958d3b0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/qml/qmlengine.cpp

@@ -970,7 +970,7 @@ void QmlEngine::quitDebugger()
 
 void QmlEngine::doUpdateLocals(const UpdateParameters &params)
 {
-    Q_UNUSED(params);
+    Q_UNUSED(params)
     d->updateLocals();
 }