fix pli2 e3 when timestamp_flt_b2 is not detected

Zinur gave me two cases were the analysis were signed as Passed but are now raising an exception:

hwc_test = 'PLI2.e3' 
circuit_name = 'RQ8.L1' 
campaign= 'Recommissioning 2022/2023' 
t_start = '2023-03-18 14:41:10.311000000'
t_end = '2023-03-18 15:10:20.019000000'

and

hwc_test = 'PLI2.e3' 
circuit_name = 'RQ9.R1' 
campaign= 'Recommissioning 2022/2023' 
t_start = '2023-03-18 14:41:10.287000000'
t_end = '2023-03-18 15:15:49.697000000'

The main issue was not really the exception but the fact that the exception was in the query part, meaning that none of the signals were not plotable in the notebook. This MR merges that by making all the timestamps optional.

I also added a test to show that behaviour.