fix(xo-server/clearHost): explicit message on missing migration network

Fixes zammad#14882

CHANGELOG.unreleased.md

@@ -13,7 +13,8 @@
 
 > Users must be able to say: “I had this issue, happy to know it's fixed”
 
-- [Incremental Replication] Fix task showing as *interrupted* when running without health check [Forum#62669](https://xcp-ng.org/forum/post/62669) (PR [#6866](https://github.com/vatesfr/xen-orchestra/pull/6866))
+- [Incremental Replication] Fix task showing as _interrupted_ when running without health check [Forum#62669](https://xcp-ng.org/forum/post/62669) (PR [#6866](https://github.com/vatesfr/xen-orchestra/pull/6866))
+- [Host evacuation] Better error message when migration network no longer exists
 
 ### Packages to release
 

packages/xo-server/src/xapi/index.mjs

@@ -182,8 +182,15 @@ export default class Xapi extends XapiBase {
   async clearHost({ $ref: hostRef, $pool: pool }, force) {
     await this.call('host.disable', hostRef)
 
-    const migrationNetworkId = pool.other_config['xo:migrationNetwork']
-    const migrationNetworkRef = migrationNetworkId && this.getObject(migrationNetworkId).$ref
+    const migrationNetworkRef = (id => {
+      if (id !== undefined) {
+        const network = this.getObject(id, undefined)
+        if (network === undefined) {
+          throw new Error('could not find migration network ' + id)
+        }
+        return network.$ref
+      }
+    })(pool.other_config['xo:migrationNetwork'])
     try {
       try {
         await (migrationNetworkRef === undefined