Negative fund income means that the investor's principal is losing money, not that the investor wants to give money. Funds generally do not lose money, so there is no case of money being deducted. Because funds generally don't invest with leverage, and no matter how stocks fall, they generally don't fall to 0.

After investors buy a fund, they all hold the corresponding fund shares. The rise and fall of the fund is the rise and fall of the net value, and the rise and fall of the net value does not affect the number of investors' shares. General fund net value will not fall to zero.