Fix loading execution of wrong replica

Fixes an issue where the execution ID of the previously visited replica
was used to load the execution of the current replica.

This commit makes sure that old execution ID is cleared before leaving
the replica details page.

src/stores/ReplicaStore.ts

@@ -131,6 +131,7 @@ class ReplicaStore {
 
   @action clearDetails() {
     this.replicaDetails = null;
+    this.currentlyLoadingExecution = "";
   }
 
   @action getReplicasSuccess(replicas: ReplicaItem[]) {