Could not find t0 or t0 found; using initial t0 = 4908 instead of 1

[kingljy0818]

Dear all. Recently, I have perform several yank tests, and encountered a problem in the end of yank calculation logs. There are two cases of yank's calculation results, one can find t0, and one can't find t0, but in both cases, you can use yank analyze to obtain the result of free energy. In any case, the result of free energy is more credible，can find t0 or can't find t0 ?