Check server presence support and comment code

src/gui/MainPane/AccountContextMenu.qml

@@ -56,6 +56,7 @@ HMenu {
     }
 
     HMenuItem {
+        visible: presence
         enabled: presence !== "unavailable" && firstSyncDone
         icon.name: "user-presence"
         icon.color: theme.controls.presence.unavailable
@@ -64,6 +65,7 @@ HMenu {
     }
 
     HMenuItem {
+        visible: presence
         enabled: presence !== "invisible" && firstSyncDone
         icon.name: "user-presence"
         icon.color: theme.controls.presence.offline

src/gui/MainPane/AccountDelegate.qml

@@ -137,7 +137,9 @@ HTile {
 
     contextMenu: AccountContextMenu {
         userId:        model.id
-        presence:      model.presence
+        presence:      model.presence_support ? model.presence : null
+
+        // Gray out buttons before first sync
         firstSyncDone: model.first_sync_done
     }