It looks like the Riot mission won't start because global variable $58, a variable used by the Flow control script to flag that the riot mission has already been launched, has been altered. Judging by the values stored in this and similar unnamed global variables, your save has been corrupted by a bad script that has added over 50 parked car generators to your save.
Removing the bad mod won't fix the problem with your corrupt variables. You'll need to reset $58 = 0 or the mission won't launch. SASE has a Script tool that can edit global variables.
Resetting $58 should allow the Riot mission to start, but it looks like quite a few other variables have been corrupted as well. A lot of the damage won't make a difference this late in the game, but other damage might. I wouldn't be surprised if you ran into other problems related to this issue.