Take MessageManagerLock in FocusTraverser and KeyboardFocusTraverser unit tests

modules/juce_gui_basics/components/juce_FocusTraverser.cpp

@@ -172,6 +172,7 @@ struct FocusTraverserTests  : public UnitTest
     void runTest() override
     {
         ScopedJuceInitialiser_GUI libraryInitialiser;
+        const MessageManagerLock mml;
 
         beginTest ("Basic traversal");
         {

modules/juce_gui_basics/keyboard/juce_KeyboardFocusTraverser.cpp

@@ -103,6 +103,7 @@ struct KeyboardFocusTraverserTests  : public UnitTest
     void runTest() override
     {
         ScopedJuceInitialiser_GUI libraryInitialiser;
+        const MessageManagerLock mml;
 
         beginTest ("No child wants keyboard focus");
         {