[gnome-flashback] monitor-manager: Fix output ids returned by GetResources.

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3a43465409b3c41685e896b423f4998f26692be3
Author: Ignacy Gawędzki <bugs qult net>
Date:   Tue May 15 22:05:47 2018 +0200

    monitor-manager: Fix output ids returned by GetResources.
    
    Just like 63163777a205447105369e195e2ceda1a64ee613 introduced the same
    bug as in Mutter, this needs to be fixed the same way as:
    https://gitlab.gnome.org/GNOME/mutter/commit/5ad34e0e
    
    Signed-off-by: Ignacy Gawędzki <bugs qult net>
    Signed-off-by: Ignacy Gawędzki <ignacy gawedzki green-communications fr>

 backends/gf-monitor-manager.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/backends/gf-monitor-manager.c b/backends/gf-monitor-manager.c
index 916977a..aede740 100644
--- a/backends/gf-monitor-manager.c
+++ b/backends/gf-monitor-manager.c
@@ -1141,7 +1141,7 @@ gf_monitor_manager_handle_get_resources (GfDBusDisplayConfig   *skeleton,
                              NULL /* properties */);
     }
 
-  for (l = manager->outputs; l; l = l->next)
+  for (l = manager->outputs, i = 0; l; l = l->next, i++)
     {
       GfOutput *output = l->data;
       GVariantBuilder crtcs, modes, clones, properties;