choose first db if none selected

packages/builder/src/nav/DatabasesList.svelte

@@ -1,5 +1,5 @@
 <script>
-  import { tick } from "svelte"
+  import { tick, onMount } from "svelte"
   import { store, backendUiStore } from "../builderStore"
   import api from "../builderStore/api"
   import getIcon from "../common/icon"
@@ -25,6 +25,12 @@
       return state
     })
   }
+
+  onMount(() => {
+    if ($store.appInstances.length > 0) {
+      selectDatabase($store.appInstances[0]);
+    }
+  })
 </script>
 
 <div class="root">