fix: TypeError: reduce() of empty iterable with no initial value

[AstroGD]

Hey there,
I am unsure if this is only an issue on my end but I am encountering the following error:

Traceback (most recent call last):
  File ".../compress/scripts/yosys2compress.py", line 356, in <module>
    add_ports_definition(circuit_compress_lines, dic_ports)
  File ".../compress/scripts/yosys2compress.py", line 319, in add_ports_definition
    controls_str_port_sigs = ft.reduce(lambda a, b: a+' '+b, ports_cfg["controls"].keys())
TypeError: reduce() of empty iterable with no initial value

The line in question is

controls_str_port_sigs = ft.reduce(lambda a, b: a+' '+b, ports_cfg["controls"].keys())

When processing the canright_aes_sbox_opt make script from the artifact of your paper, it seems like this dictionary stays empty for me (I dont know if this is supposed to happen?)

Therefore I am proposing this change to fix the error and handle possibly empty dictionaries.
Have a nice day ^^