macOS: yet another fix of line drawing (#1409)

The call to fixloop() had been accidentally removed by previous commits.

This commit fixes it to prevent potential regressions in *other* code
(not directly related to symbol drawing).

src/drivers/Quartz/Fl_Quartz_Graphics_Driver_vertex.cxx

@@ -34,6 +34,7 @@ void Fl_Quartz_Graphics_Driver::end_points() {
 }
 
 void Fl_Quartz_Graphics_Driver::end_loop() {
+  fixloop();
   end_line_or_loop(true);
 }