Conditionals for blank or deleted values?

[versatilehuman]

• Blank value in maintenance_div in points_of_interest junked the poi alerts page.
• Deleted user is preventing export of alerts (Alert history no longer exporting #248)

Are there any other places we need to implement conditionals to tighten things up?

[gisdevcc]

A fix for the maintenance_div in poi alertts issue is fixed with fpdcc/trailsyserver@9ab09c0

Deferring larger review for later