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/qmlprofiler/debugmessagesmodel.cpp

@@ -95,7 +95,7 @@ int DebugMessagesModel::expandedRow(int index) const
 
 int DebugMessagesModel::collapsedRow(int index) const
 {
-    Q_UNUSED(index);
+    Q_UNUSED(index)
     return Constants::QML_MIN_LEVEL;
 }