fix(xo-server-audit): handle non-existent XOA plugin (#5239)

See https://github.com/vatesfr/xen-orchestra/commit/38de5048bc2f867944546337d4a464ed19eb51a4#commitcomment-41875481

CHANGELOG.unreleased.md

@@ -30,4 +30,5 @@
 >
 > In case of conflict, the highest (lowest in previous list) `$version` wins.
 
+- xo-server-audit patch
 - xo-server patch

packages/xo-server-audit/src/index.js

@@ -312,6 +312,12 @@ class AuditXoPlugin {
   // See www-xo#344
   async _uploadLastHash() {
     const xo = this._xo
+
+    // In case of non-existent XOA plugin
+    if (xo.audit === undefined) {
+      return
+    }
+
     const chain = await xo.audit.getLastChain()
 
     let lastHash, integrityCheckSuccess