(prev commit)director will not attempt to draw if the window has area zero
(prev commit)director will not attempt to draw if the window has area zero

This change fixes crashes in tests
test_fadeouttiles_tr.py
test_accel_amplitude.py
and probably others:

If you minimized the window when the transition has ended, the app crashed with:
 [snip]
 File "H:\cocos_pristine\cocos_dev\cocos_released\test\..\cocos\grid.py", line
170, in _set_3d_projection
 gluPerspective(60, 1.0*width/height, 0.1, 3000.0)
ZeroDivisionError: float division

When minimized, at least in windows, you have director.windows.height==0, thus crashing
But there is no reason to draw if the window area is zero. 
google-code-export/los-cocos,google-code-export/los-cocos