Errors pop-up when not on a DK

[Hanzo55]

When logging on to a player other than a DK, this pops:

Message: Interface\AddOns\DKIDiseases\DKIDiseases.lua:308: attempt to index field '?' (a nil value)
Time: 09/10/16 17:48:23
Count: 1
Stack: Interface\AddOns\DKIDiseases\DKIDiseases.lua:308: in function `DKIDiseases_OnLoad'
Interface\AddOns\DKIDiseases\DKIDiseases.lua:1240: in main chunk

Locals: self = DKIDiseasesFrame {
 0 = <userdata>
}
_ = "Demon Hunter"
class = "DEMONHUNTER"
(for index) = 2
(for limit) = 3
(for step) = 1
i = 2
(*temporary) = nil
(*temporary) = DKIDiseasesBar1 {
 0 = <userdata>
}
(*temporary) = "attempt to index field '?' (a nil value)"
diseaseBar = <table> {
 1 = DKIDiseasesBar1 {
 }
 0 = DKIDiseasesBar0 {
 }
}