i made a research facility with a reactor core but as soon as i made it's save, and load the same one, i see this error:

[Garry's Bombs 5 Base] lua/entities/gb5_base_radiation_draw_ent_fl.lua:42: attempt to index field 'radowner' (a nil value)
1. unknown - lua/entities/gb5_base_radiation_draw_ent_fl.lua:42


this is exactly is that when i made the reactor core, i placed a uranium-235 in it at the center, but when i enter the same research facility save, the errors like that one on top can still appear. Tell me why did that error popped up in console.