diff --git a/src/components/ConcernementMapItem.vue b/src/components/ConcernementMapItem.vue
index b5cfaf5..e26bb8d 100644
--- a/src/components/ConcernementMapItem.vue
+++ b/src/components/ConcernementMapItem.vue
@@ -1393,7 +1393,7 @@ export default {
             this.paper_main_object.scale(obj.s);
 
             // update superposition constraints points
-            if (this.concernement.superposition_constraints_id.length) {
+            if (this.concernement.superposition_constraints_id && this.concernement.superposition_constraints_id.length) {
               // get all the constraints of the world
               let all_constrains = Matter.Composite.allConstraints(this.matterEngine.world);
               // loop through all constraint ids recorded in the concernement
@@ -1480,7 +1480,7 @@ export default {
             this.paper_main_object.scale(obj.s);
             
             // update superposition constraints points
-            if (this.concernement.superposition_constraints_id.length) {
+            if (this.concernement.superposition_constraints_id && this.concernement.superposition_constraints_id.length) {
               // get all the constraints of the world
               let all_constrains = Matter.Composite.allConstraints(this.matterEngine.world);
               // loop through all constraint ids recorded in the concernement
@@ -1536,7 +1536,10 @@ export default {
       }
 
       if (this.opened_concernement) {
-        if (this.opened_concernement.id !== this.id && this.opened_concernement.superposed_concernements_id.indexOf(this.id) < 0) {
+        if (
+          this.opened_concernement.id !== this.id 
+          && (!this.opened_concernement.superposed_concernements_id || this.opened_concernement.superposed_concernements_id.indexOf(this.id) < 0)
+        ) {
           this.pushAside()
         }
       } else if (this.map_mode === 'proximite'