Cannot use POLAR Code Configurator in GRC anymore

[jdemel]

In current GR3.7 versions, if you add 'POLAR Code Configurator' to a flowgraph in GRC, it freezes. GRC is unresponsive and one thread is running at 100%. The block calls a python function 'gnuradio.fec.polar.load_frozen_bits_info', which handles initialization parameters.

This construction used to work in older GR versions, when polar codes were added. Also, if you import gnuradio.fec.polar in a python shell and call the function, it does return the expected value.

I tried to exclude errors in the functions themselves and added some more prints.
Thus, I enforced the is_prototype=True parameter as well as channel="BEC". Now, if you open GRC, add a new flowgraph and try to add the 'POLAR code Configurator', you can observe print outs, I added, at the beginning and the end of the load_frozen_bits_info. The function gets called twice. Thus, I assume it did not throw an error. Still, GRC freezes.

So far, I assume some change in GRC broke this configurator feature.

tested with:
3.7.12git-99-g082711cc
v3.7.10.1-158-gedd02537
on different systems.

[jdemel]

The bug fix is merged into maint. Thus, I close the issue now.