[BUG] Can't apply Vaporsynth Knlmeanscl filter to all planes

[Selur]

I checked the script that Hybrid generates,
with channel

• 'auto'
  
  clip = core.knlm.KNLMeansCL(clip=clip)
• 'Y'
  
  clip = core.knlm.KNLMeansCL(clip=clip, channels="Y")
• 'UV'
  
  clip = core.knlm.KNLMeansCL(clip=clip, channels="UV")
• 'YUV'
  
  clip = core.knlm.KNLMeansCL(clip=clip, channels="YUV")
• 'RGB'
  
  clip = core.knlm.KNLMeansCL(clip=clip, channels="RGB")
  But this causes a an error:
  
  Python exception: knlm.KNLMeansCL: 'channels' must be 'YUV', 'Y', or 'UV' with YUV color space!
  -> I'll fix that, but other than that I see no issue with the script created by Hybrid.
  

Cu Selur