add error message for editing outing.participant_count
add error message for editing outing.participant_count

c2corg/v6_ui,c2corg/v6_ui,Courgetteandratatouille/v6_ui,c2corg/v6_ui,olaurendeau/v6_ui,olaurendeau/v6_ui,olaurendeau/v6_ui,c2corg/v6_ui,Courgetteandratatouille/v6_ui,Courgetteandratatouille/v6_ui,Courgetteandratatouille/v6_ui,olaurendeau/v6_ui