Projucer: Fix potential order-of-destruction bug in AvailableModulesList

When the AvailableModulesList is destroyed, it will wait for the current
module scanning job (running on a background thread) to complete. This
job will try to take the AvailableModulesList::lock when it completes,
so the lock must outlive the background thread.

extras/Projucer/Source/Project/Modules/jucer_AvailableModulesList.h

@@ -169,10 +169,10 @@ private:
     }
 
     //==============================================================================
-    std::future<void> scanner;
     ModuleIDAndFolderList modulesList;
     ListenerList<Listener> listeners;
     CriticalSection lock;
+    std::future<void> scanner;
 
     //==============================================================================
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AvailableModulesList)