[evolution-data-server] Vala: Mark the message field of CamelFolderThreadNode as nullable

[Corentin Noël <corentinnoel src gnome org>]

commit c335740540704be6e7de3dda296d5ca1fe0e28af
Author: Corentin Noël <corentin elementary io>
Date:   Tue Dec 29 14:26:01 2020 +0100

    Vala: Mark the message field of CamelFolderThreadNode as nullable

 src/vala/Camel-1.2.metadata | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/vala/Camel-1.2.metadata b/src/vala/Camel-1.2.metadata
index c29dccf21..8c94ca7f2 100644
--- a/src/vala/Camel-1.2.metadata
+++ b/src/vala/Camel-1.2.metadata
@@ -124,6 +124,7 @@ FolderThread.tree type="Camel.FolderThreadNode"
 FolderThreadNode.next type="unowned Camel.FolderThreadNode?"
 FolderThreadNode.parent type="unowned Camel.FolderThreadNode?"
 FolderThreadNode.child type="unowned Camel.FolderThreadNode?"
+FolderThreadNode.message nullable
 
 // FILE* are supported by Vala
 StoreSummary.* skip=false