fix: review feedback

Signed-off-by: romanetar <roman_ag@hotmail.com>

Author: romanetar

app/Services/Model/Imp/PresentationCategoryGroupService.php

@@ -262,6 +262,7 @@ public function disassociateTrack2TrackGroup(Summit $summit, $track_group_id, $t
             // been called yet at this point.
             foreach ($presentations as $presentation) {
                 $selection_plan = $presentation->getSelectionPlan();
+                if (is_null($selection_plan)) continue;
                 $track_reachable_via_another_group = $selection_plan->getCategoryGroups()->exists(
                     function ($key, $group) use ($track, $track_group) {
                         return $group->getId() !== $track_group->getId()

tests/oauth2/OAuth2TrackGroupsApiTest.php

@@ -377,6 +377,67 @@ public function testDisassociateTrack2TrackGroup(){
         }
     }
 
+    public function testDisassociateTrackFromTrackGroupPreservesSelectionPlanWhenTrackReachableViaAnotherGroup()
+    {
+        // Set up a second category group (TrackGroupB) that also contains $defaultTrack
+        // and belongs to the same $default_selection_plan as $defaultTrackGroup (TrackGroupA).
+        // Removing $defaultTrack from TrackGroupA should NOT clear the selection plan on
+        // presentations because TrackGroupB still covers the track within the same plan.
+        $track_group_b = new \models\summit\PresentationCategoryGroup();
+        $track_group_b->setName("TRACK GROUP B");
+        $track_group_b->addCategory(self::$defaultTrack);
+        self::$summit->addCategoryGroup($track_group_b);
+        self::$default_selection_plan->addTrackGroup($track_group_b);
+        self::$em->persist($track_group_b);
+        self::$em->flush();
+
+        $headers = [
+            "HTTP_Authorization" => " Bearer " . $this->access_token,
+            "CONTENT_TYPE"       => "application/json"
+        ];
+
+        $params = [
+            'id'             => self::$summit->getId(),
+            'track_group_id' => self::$defaultTrackGroup->getId(),
+            'track_id'       => self::$defaultTrack->getId()
+        ];
+
+        // Only collect presentations that belong to $default_selection_plan — the plan
+        // that has TrackGroupB as a second group covering $defaultTrack.
+        // Presentations of $default_selection_plan2 are intentionally excluded: that plan
+        // only has $defaultTrackGroup, so their selection plan will be correctly cleared.
+        $presentations = self::$defaultTrack->getPresentationsBySelectionPlanIds(
+            [self::$default_selection_plan->getId()]
+        );
+        $this->assertNotEmpty($presentations);
+        foreach ($presentations as $presentation) {
+            $this->assertTrue($presentation->getSelectionPlanId() > 0);
+        }
+        $presentation_ids = array_map(fn($p) => $p->getId(), $presentations);
+
+        // disassociate $defaultTrack from TrackGroupA
+        $response = $this->action(
+            "DELETE",
+            "OAuth2PresentationCategoryGroupController@disassociateTrack2TrackGroup",
+            $params,
+            [],
+            [],
+            [],
+            $headers
+        );
+
+        $this->assertResponseStatus(204);
+
+        // reset EM and re-fetch presentations — selection plan must be preserved
+        // because TrackGroupB still contains $defaultTrack within the same plan
+        self::$em = \LaravelDoctrine\ORM\Facades\Registry::resetManager(\models\utils\SilverstripeBaseModel::EntityManager);
+        foreach ($presentation_ids as $id) {
+            $presentation = self::$em->find(\models\summit\Presentation::class, $id);
+            $this->assertNotNull($presentation);
+            $this->assertGreaterThan(0, $presentation->getSelectionPlanId());
+        }
+    }
+
     public function testAddPrivateTrackGroup(){
         $params = [
             'id' => self::$summit->getId(),