Fixed "ZeroDivisionError: float division by zero" when minimized adding simple "ifs" on def set_2d and def set_3d

Fixed "ZeroDivisionError: float division by zero" when minimized.
Traceback (most recent call last):
  File "MCMain.py", line 484, in <module>
    main()
  File "MCMain.py", line 481, in main
    pyglet.app.run()
  File "C:\Python27\lib\site-packages\pyglet\app\__init__.py", line 264, in run
    EventLoop().run()
  File "C:\Python27\lib\site-packages\pyglet\app\win32.py", line 63, in run
    self._timer_func(0, 0, timer, 0)
  File "C:\Python27\lib\site-packages\pyglet\app\win32.py", line 84, in _timer_func
    sleep_time = self.idle()
  File "C:\Python27\lib\site-packages\pyglet\app\__init__.py", line 193, in idle
    window.dispatch_event('on_draw')
  File "C:\Python27\lib\site-packages\pyglet\window\__init__.py", line 1219, in dispatch_event
    EventDispatcher.dispatch_event(self, *args)
  File "C:\Python27\lib\site-packages\pyglet\event.py", line 349, in dispatch_event
    return getattr(self, event_type)(*args)
  File "MCMain.py", line 434, in on_draw
    self.set_3d()
  File "MCMain.py", line 424, in set_3d
    gluPerspective(65.0, width / float(height), 0.1, 60.0)
ZeroDivisionError: float division by zero