Chatty spends a lot of time writing PNGs on each message

I have no slightest clue what's going on there, but I'm seeing about 1-2 second UI freezes when sending or receiving messages in Chatty. To try to find out why, I tried profiling in sysprof - and it turns out that Chatty spends all that time in libpng writing rows of some PNG image in some idle handler with libhandy in its stack trace:

Trace: capture.syscap

Observed on Chatty 0.4.0-1pureos1

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