[pluggo] trouble with average~ object in multi channel sidechain plugin

I'm making a simple compressor with an additional stereo sidechain input, which i'm using in Live.

my compressor works fine as a standalone.

when i connect it up in live, i have a problem. if the audio played into the sidechain input of my plugin (channels 3 and 4) is intermittent, that is if i turn a clip played into the sidechain on and off, or if i'm playing a sequence of samples that have silence between them into the sidechain, the calculations made by the average~ object go wrong. when it seems like the level in is of value zero i get "nan" values out of the average~ object, when it should be giving me a value of zero. this causes the whole of abletons audio to cut out intermittently. 

has anyone come across this kind of thing? 

thanks


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