last trial has ITI_stop_time as NaN, but stop_time has a value

[arjunsridhar12345]

Title is self explanatory. Last trial stop time is being set to ITI_start_time if there is not ITI_stop_time for the last trial. should be a pretty straightforward fix

[arjunsridhar12345]

Originating issue here: https://github.com/AllenNeuralDynamics/DF-Refactoring/issues/164