it calculates the net income for gold and food as being -x even if you have 0 on you. This throws out the family total nets as well as empire nets on the list as if you have 0 gold, you are not actually paying building or fleet cost and so your whole family is not losing that x gold.
For example:
Empire 1 current gold: 10k
Empire 1 Net income: 50k gold
Empire 2 current gold: 0
Empire 2 Net income: -10k gold (should be 0)
Displayed Family Net income: 40k gold (should be 50k because as a family you have indeed gained 50k gold (hence why people choose to have 0 gold/food and slowly lose fleet rather than pay the upkeep))