Web: show "select a job" when the first job is submitted

Hide the "get the add-on" and show the "select a job" when the first job
has been submitted.

web/app/src/stores/jobs.js

@@ -36,6 +36,9 @@ export const useJobs = defineStore('jobs', {
     },
   },
   actions: {
+    setIsJobless(isJobless) {
+      this.$patch({ isJobless: isJobless });
+    },
     setActiveJobID(jobID) {
       this.$patch({
         activeJob: {id: jobID, settings: {}, metadata: {}},

web/app/src/views/JobsView.vue

@@ -143,6 +143,7 @@ export default {
     // SocketIO data event handlers:
     onSioJobUpdate(jobUpdate) {
       this.notifs.addJobUpdate(jobUpdate);
+      this.jobs.setIsJobless(false);
 
       if (this.$refs.jobsTable) {
         if (jobUpdate.previous_status)