(svn r25546) -Fix: two small memory leaks

src/viewport.cpp

@@ -165,6 +165,9 @@ static Point MapXYZToViewport(const ViewPort *vp, int x, int y, int z)
 
 void DeleteWindowViewport(Window *w)
 {
+	if (w->viewport == NULL) return;
+
+	delete w->viewport->overlay;
 	free(w->viewport);
 	w->viewport = NULL;
 }