Caused by 1c0f374ec3
When `EDBM_edge_find_nearest_ex` does not find a nearest edge in
`loopcut_mouse_move`, then `loopcut_update_edge` will set
`RingSelOpData` `ob` to nullptr (rightfully so).
This would then crash in `ringsel_draw` (because we are trying to call
`object_to_world()` on the nullptr.
Prior to 1c0f374ec3 this was also "wrong", but
`EDBM_preselect_edgering_draw` would early out before using garbage
data.
Now guard against this and dont call `EDBM_preselect_edgering_draw` at
all if we dont have valid input.
Philipp Oeser