C2-25226: Fix OpenFin unregistered intent listener (#2282)

Author: antoinerollindev

src/app/openfin-handler.ts

@@ -115,10 +115,11 @@ export class OpenfinHandler {
    */
   public async unregisterIntentHandler(uuid: UUID) {
     const subscription = this.intentHandlerSubscriptions.get(uuid);
-
-    const response = await subscription.unsubscribe();
-    this.intentHandlerSubscriptions.delete(uuid);
-    return response;
+    if (subscription) {
+      const response = await subscription.unsubscribe();
+      this.intentHandlerSubscriptions.delete(uuid);
+      return response;
+    }
   }
 
   /**