video.preview() has a bug after concatenate_videoclips in version 1.0.3

[ShubinZheng]

this is my python code
`from moviepy.editor import VideoFileClip, concatenate_videoclips

video_clip1 = VideoFileClip("video1.mp4")
video_clip2 = VideoFileClip("video2.mp4")

final_video = concatenate_videoclips([video_clip1, video_clip2])

final_video.preview()`
when running, there's an exception:

the class CompositeAudioClip has no attribute 'fps'
and I modify the init of CompositeAudioClip

and it works. when write_videofile() it doesn't have this bug, but preview() has this bug.
also find in version 2.0.1-dev