Change rendering engine during render crashs Fr0st

[Luis Gonzaga]

How to reproduce the bug:

1) Choose flam4 rendering engine;
2) Choose one flame and start render;
3) While render is running go to File > Preferences > Rendered tab and change to flam3.

Fr0st will generate the following error message:

Traceback (most recent call last):
Exception in thread bgRenderLoop:
Traceback (most recent call last):
File “threading.pyc’, line 523, in _bootstrap_inner
File “threading.pyc”, line 477, in run
File “fr0stlib\decorators.pyc”, line 67, in wrapper
File “fr0stlib\gui\rendererpyc’, line 105, in bgRenderLoop
File “fr0stlib\decorators.pyc”, line 67, in wrapper
File “fr0stlib\gui\renderer.pyc”, line 135, in process
File “fr0stlib\gui\renderer.pyc’, line 153, in OnlmageReady
File “wx\_gdi.pyc’, line 908, in BitmapFromBufferRGBA
TypeError: expected a readable buffer object