saveguard against deregistering from an alredy destroyed session

src/lib/element-tracker.hpp

@@ -181,6 +181,7 @@ namespace lib {
       void
       detach()
         {
+          if (!getRegistry) return;
           TAR& element = static_cast<TAR&> (*this);
           
           getRegistry().remove(element);
@@ -222,6 +223,12 @@ namespace lib {
           establishRegistryLink (accessInstance);
         }
       
+      static void
+      deactivateRegistryLink()
+        {
+          getRegistry = RegistryLink();  // empty accessor function
+        }
+      
     protected:
       static RegistryLink getRegistry;
     };

src/proc/mobject/session/session-interface-modules.hpp

@@ -101,6 +101,7 @@ namespace session {
       SequenceTracker sequenceRegistry_;
       
       SessionInterfaceModules();
+     ~SessionInterfaceModules();
     };
   
   
@@ -116,6 +117,14 @@ namespace session {
     asset::Sequence::setRegistryInstance (sequenceRegistry_);
   }
   
+  inline
+  SessionInterfaceModules::~SessionInterfaceModules()
+  {
+    asset::Sequence::deactivateRegistryLink();
+    asset::Timeline::deactivateRegistryLink();
+  }
+  
+  
   
 }} // namespace mobject::session
 #endif

tests/components/proc/mobject/session/session-element-tracker-test.cpp

@@ -200,6 +200,19 @@ namespace test    {
           CHECK (num_timelines + 1 == sess->timelines.size());
           CHECK (anotherTimeline == sess->timelines[num_timelines]);    // moved to the previous slot
           CHECK (specialTimeline.use_count() == 1);                     // we're holding the last reference
+          
+          verify_cleanup (anotherTimeline);
+        }
+      
+      
+      /** @test ensure the asset cleanup doesn't interfere with session shutdown
+       */
+      void
+      verify_cleanup (PTimeline aTimeline_in_session)
+        {
+          REQUIRE (1 < aTimeline_in_session.use_count(), "test object should still be attached to session");
+          Session::current.reset();
+          aTimeline_in_session->detach();           // should be a no-op and not cause any invalid access
         }
     };