Clear selected app ID from overview store when unmounting, and avoid sending up 'null' and 'undefined' string app ID headers

packages/builder/src/api.js

@@ -10,11 +10,10 @@ import { auth, overview } from "./stores/portal"
 export const API = createAPIClient({
   attachHeaders: headers => {
     // Attach app ID header from store
-    let appId = get(store).appId
-    if (!appId) {
-      appId = get(overview).selectedAppId
+    let appId = get(store).appId || get(overview).selectedAppId
+    if (appId) {
+      headers["x-budibase-app-id"] = appId
     }
-    headers["x-budibase-app-id"] = appId
 
     // Add csrf token if authenticated
     const user = get(auth).user

packages/builder/src/pages/builder/portal/overview/[appId]/_layout.svelte

@@ -33,7 +33,7 @@
   import * as routify from "@roxi/routify"
   import { onDestroy } from "svelte"
 
-  // Keep URL and state in sync for selected screen ID
+  // Keep URL and state in sync for selected app ID
   const stopSyncing = syncURLToState({
     urlParam: "appId",
     stateKey: "selectedAppId",
@@ -111,6 +111,10 @@
   onDestroy(() => {
     stopSyncing()
     store.actions.reset()
+    overview.update(state => ({
+      ...state,
+      selectedAppId: null,
+    }))
   })
 </script>