Integrate ClearSurfacesCmd into Application

src/Application/Application.cpp

@@ -63,7 +63,9 @@ void Application::onKeyPressed(ofKeyEventArgs & args){
 	if(_keySequence.size() >= 3){
 		_keySequence = _keySequence.substr(_keySequence.size() - 3, 3);
 		if(_keySequence == "new"){
-			_cmdManager.exec(new ClearSurfacesCmd());
+			if(SurfaceStack::instance()->size()){
+				_cmdManager.exec(new ClearSurfacesCmd(getSurfaceManager()));
+			}
 			return;
 		}
 	}

src/Application/Application.h

@@ -15,6 +15,7 @@
 #include "Info.h"
 
 #include "SurfaceManagerGui.h"
+#include "SurfaceStack.h"
 
 // TODO: To be removed.
 #include "GuiMode.h"