Solve the issue of adding event data for SANS2D

The problem was a vector overflow. This correct the problem

re #6594
Revert "Do not load event data for adding data"

This reverts commit 46dde6dddb9b2fd2a979af6a067c5d48bc5e8250.
Commit related to #6986

re #6594
Merge branch 'feature/6594_add_sans2d_ev' into develop