Fix add Group Member noise (NOJIRA)

app/src/Model/Table/GroupMembersTable.php

@@ -188,10 +188,17 @@ public function buildRules(RulesChecker $rules): RulesChecker {
    * @return string         Display field
    */
 
-  public function generateDisplayField(GroupMember $entity): string {
-    // Pull the group and person information to build a more useful display string
-
-    return __d('field', 'group_membership', [$entity->person->primary_name->full_name, $entity->group->name]);
+  public function generateDisplayField(GroupMember $entity): ?string {
+    // Pull the group and person information to build a more useful display string.
+    // Note because there is no setAddContains() (this is probably the only place
+    // where it would be useful if it were even conceptually a thing) we can't assume
+    // we have any entity information here.
+
+    if(!empty($entity->person->primary_name)) {
+      return __d('field', 'group_membership', [$entity->person->primary_name->full_name, $entity->group->name]);
+    }
+
+    return null;
   }
 
   /**
@@ -575,6 +582,10 @@ public function saveAttributeCollectorPetitionAttributes(int $personId, array $f
       $member[$fld->enrollment_attribute->attribute] = $fld->value;
     }
 
+    if(!isset($member['group_id'])) {
+      return null;
+    }
+
     return $this->saveOrFail($this->newEntity($member));
   }
 }