My understanding is that at least some of your SSD benefits can be taxable, and therefore are properly reported on FAFSA line 45.i.
It is worth noting that Social Security Disability benefit payments are taxed differently than other income. Generally speaking, only half of your Social Security Disability benefit payments are counted as taxable income.
http://www.disabilitybenefitscenter.org/faq/social-security-disability-benefits-taxes