AUP3: Don't molest project file when applying macros

Cliff reported that if you apply a macro to "Files" and you had
a "saved project" open at the time, you would get the "not saved
properly" dialog when you next open that "saved project".

This should correct it...

src/ProjectManager.cpp

@@ -920,11 +920,12 @@ void ProjectManager::ResetProjectToEmpty() {
 
    WaveTrackFactory::Reset( project );
 
-   projectFileManager.Reset();
-
    projectHistory.SetDirty( false );
    auto &undoManager = UndoManager::Get( project );
    undoManager.ClearStates();
+
+   projectFileManager.CloseProject();
+   projectFileManager.OpenProject();
 }
 
 void ProjectManager::RestartTimer()