Doesnt matter... the water will be drawn into the filter as Yuta says, concider the heater clips - they are in direct contact with the heater body, and they dont melt !
In fact, you can have the heater INSIDE the filter, and you can have an inline one that fits onto the filter pipe ! So I wouldnt worry about it ;-)
I think I would rather have the filter OUTLET "blowing" the heated water around the tank, than sucking it into the filter - as it may be too warm for the bacteria, but Im just thinking aloud here.