[Discuss-gnuradio] free(): invalid pointer for AM demod block at Gnuradio 3.7.13.5

I'm running Arch Linux with Gnu Radio 3.7.13.5 and
Python 2.7.16 (default, Mar 11 2019, 18:59:25)
[GCC 8.2.1 20181127] on linux2

and if I try to use AM demod block with anything the flowgraph crashes
with this:

>>> Warning: This flow graph may not have flow control: no audio or RF hardware blocks found. Add a Misc->Throttle block to your flow graph to avoid CPU congestion.

Executing: /usr/bin/python2 -u /home/feanor/Development/SDR/top_block.py

free(): invalid pointer

>>> Done

This is just a AM demod block with null sink and null source attached
to it, reproduction flowgraph is attached to this email