fix: fixing outputs.tf for backend for apphub check (#525)

Author: amrkk123

modules/backend/outputs.tf

@@ -32,12 +32,14 @@ output "backend_service_info" {
 }
 
 output "apphub_service_uri" {
-  value = [
-    {
-      service_uri = "//compute.googleapis.com/${google_compute_backend_service.default[0].id}"
-      service_id  = substr("${google_compute_backend_service.default[0].name}-${md5("global-be-service-${var.project_id}")}", 0, 63)
-      location    = "global"
-    }
-  ]
+  value = concat(
+    !local.is_backend_bucket ? [
+      {
+        service_uri = "//compute.googleapis.com/${google_compute_backend_service.default[0].id}"
+        service_id  = substr("${google_compute_backend_service.default[0].name}-${md5("global-be-service-${var.project_id}")}", 0, 63)
+        location    = "global"
+      }
+    ] : [],
+  )
   description = "Service URI in CAIS style to be used by Apphub."
 }