Crash with SRCurrent normalization

Dataset: /data/visitor/in1153/bm05/20221115/0.36um_C_wofurnace_wd_wf_worefill/0.36um_C_wofurnace_wd_wf_worefill_0001/036um_C_wofurnace_wd_wf_worefill_0001_1_1.nx

All SRCurrent-related code should be made more robust!