[bug] public list of plans fails to render if a group has no plans

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Fix a bug: unable to filter by multiple user IDs in OpenAPI
 - Fix a bug: do not display two empty categories in the plan creation form
 - Fix a bug: do not return to the home page when clicking on previous in the machine description page
+- Fix a bug: public list of plans fails to render if a group has no plans
 - Tests for OpenAPI user trainings
 - [TODO DEPLOY] `rails db:seed`
 - [TODO DEPLOY] `rails fablab:maintenance:rebuild_stylesheet`

app/frontend/src/javascript/components/plans/plans-list.tsx

@@ -231,7 +231,7 @@ const PlansList: React.FC<PlansListProps> = ({ onError, onPlanSelection, onLogin
         return (
           <div key={groupId} className="plans-per-group">
             <h2 className="group-title">{ groupName(groupId) }</h2>
-            {renderPlansByCategory(plansByGroup)}
+            {plansByGroup && renderPlansByCategory(plansByGroup)}
           </div>
         )
       })}