Handle the case in which loaded data is incompatible with current ver…

…sion

js/pivx_shield.ts

@@ -283,11 +283,17 @@ export class PIVXShield {
       shieldData.commitmentTree,
     );
     pivxShield.mapNullifierNote = new Map(
-      Object.entries(shieldData.mapNullifierNote),
+      Object.entries(shieldData.mapNullifierNote ?? {}),
     );
     pivxShield.diversifierIndex = shieldData.diversifierIndex;
     pivxShield.unspentNotes = shieldData.unspentNotes;
-    return pivxShield;
+
+    // Shield activity update: mapNullifierNote must be present in the shieldData
+    let success = true;
+    if (!shieldData.mapNullifierNote) {
+      success = false;
+    }
+    return { pivxShield, success };
   }
 
   /**
@@ -568,6 +574,7 @@ export class PIVXShield {
     this.unspentNotes = [];
     this.pendingSpentNotes = new Map();
     this.pendingUnspentNotes = new Map();
+    this.mapNullifierNote = new Map();
   }
 }