SystematicsError : Systematics not supported for pdlabel=none

Dear Sir,
I want to run systematics computation and i have linked the following code:
'export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/b806/work/MG5_aMC_v3.4.1/MG5_aMC_v3_4_1/HEPTools/lhapdf6_py3/lib
export PYTHONPATH=$PYTHONPATH:/home/b806/work/MG5_aMC_v3.4.1/MG5_aMC_v3_4_1/HEPTools/lhapdf6_py3/bin'

However, in the process of running the program, it still reported the warning and error:
'WARNING: program /usr/bin/python3 -O /home/b806/work/MG5_aMC_v3.4.1/MG5_aMC_v3_4_1/bin/wuyong/bin/internal/systematics.py unweighted_events.lhe.gz ./tmp_2_unweighted_events.lhe.gz --mur=0.5,1,2 --muf=0.5,1,2 --pdf=errorset --start_event=5000 --stop_event=7500 --result=./log_sys_2.txt --lhapdf_config=/home/b806/work/MG5_aMC_v3.4.1/MG5_aMC_v3_4_1/HEPTools/lhapdf6_py3/bin/lhapdf-config launch ends with non zero status: 1. Stop all computation

INFO: Running Systematics computation

Command "generate_events run_01" interrupted with error:
SystematicsError : Systematics not supported for pdlabel=none
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/home/b806/work/MG5_aMC_v3.4.1/MG5_aMC_v3_4_1/bin/wuyong/run_01_tag_1_debug.log'.
Please attach this file to your report.

INFO: storing files of previous run

INFO: Done
'
I don't know how to solve it. I'd appreciate it if you could solve it.Thank you very much.