Disciplined convex programming error: Illegal operation: {invalid} + {convex}

Hello everyone! I really need your help!
the error said “Disciplined convex programming error: Illegal operation: {invalid} + {convex}”,
the c(t,i) is a variable, and the wrong part is about c(t,i), that is T_hand(t,i-1)
and my code is

Look at the values of all the input data in the offending statement. If there is an NaN, CVX will deem that “invalid”.

If that input data arises from th e solution to a previous optimization problem, perhaps that problem was not solved, and one or more of the variables was therefore assigned NaN.

thank you very much!