feat(xen-api): work-around empty VBD#VDI XenServer issue (#3950)

CHANGELOG.unreleased.md

@@ -3,6 +3,7 @@
 ### Enhancements
 
 - [Home] Set description on bulk snapshot [#3925](https://github.com/vatesfr/xen-orchestra/issues/3925) (PR [#3933](https://github.com/vatesfr/xen-orchestra/pull/3933))
+- Work-around the XenServer issue when `VBD#VDI` is an empty string instead of an opaque reference (PR [#3950](https://github.com/vatesfr/xen-orchestra/pull/3950))
 
 ### Bug fixes
 
@@ -15,6 +16,7 @@
 
 ### Released packages
 
+- xen-api v0.24.2
 - @xen-orchestra/fs v0.6.1
 - xo-server-auth-saml v0.5.3
 - xo-server v5.35.0

packages/xen-api/src/index.js

@@ -1097,7 +1097,10 @@ export class Xapi extends EventEmitter {
           props[`update_${field}`] = function(entries) {
             return xapi.setFieldEntries(this, field, entries)
           }
-        } else if (isOpaqueRef(value)) {
+        } else if (value === '' || isOpaqueRef(value)) {
+          // 2019-02-07 - JFT: even if `value` should not be an empty string for
+          // a ref property, an user had the case on XenServer 7.0 on the CD VBD
+          // of a VM created by XenCenter
           getters[$field] = function() {
             return objectsByRef[this[field]]
           }