QmlDesigner.ImportManager: Fix comparison operator

The comparison operator was not consistent if comparing the same url.
This could trigger an assert for msvc debug builds.

Change-Id: Ia9febd7ffd7d0f4dbb64184931a526e61f020672
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>

src/plugins/qmldesigner/components/importmanager/importswidget.cpp

@@ -92,6 +92,9 @@ void ImportsWidget::removeUsedImports()
 
 static bool importLess(const Import &firstImport, const Import &secondImport)
 {
+    if (firstImport.url() == secondImport.url())
+        return firstImport.toString() < secondImport.toString();
+
     if (firstImport.url() == "QtQuick")
         return true;