X-Git-Url: https://gerrit.simantics.org/r/gitweb?p=simantics%2Fplatform.git;a=blobdiff_plain;f=bundles%2Forg.simantics.db.layer0%2Fsrc%2Forg%2Fsimantics%2Fdb%2Flayer0%2Fgenericrelation%2FExternalRequest.java;h=8cf5652ce0367f31baeca31e72c0f70425657c0c;hp=b090c4a7602170ea33f699e80cfe0a3770773c5d;hb=0d9b90834ce56b292c00b1a39850ed842c3e4d42;hpb=e5db6157fd8722c946613d4e46d7aaf6bfa92609

diff --git a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/genericrelation/ExternalRequest.java b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/genericrelation/ExternalRequest.java
index b090c4a76..8cf5652ce 100644
--- a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/genericrelation/ExternalRequest.java
+++ b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/genericrelation/ExternalRequest.java
@@ -29,17 +29,20 @@ class ExternalRequest extends ParametrizedPrimitiveRead<Pair<GenericRelationInde
         this.procedure = procedure;
         parameter.first.addListener(graph, parameter.second, this);
     }
-    
+
     @Override
     public void unregistered() {
-        parameter.first.removeListener(session, parameter.second, this);
+        // Session will be null if the listener was not added at all.
+        if (session != null) {
+            parameter.first.removeListener(session, parameter.second, this);
+        }
     }
-    
+
     @Override
     public void run() {
         synchronized(getClass()) {
             procedure.execute(value++);
         }
     }
-    
+
 }
\ No newline at end of file