[gjs: 1/2] gjs_dbus_implementation_emit_signal: don't try to unref NULL

[Philip Chimento <pchimento src gnome org>]

commit dc15ab81baf589a071b241da90e2ee83c83baef3
Author: Adam Williamson <awilliam redhat com>
Date:   Fri Aug 28 13:33:04 2020 -0700

    gjs_dbus_implementation_emit_signal: don't try to unref NULL
    
    07221d6d (which added support for multiple bus connections)
    added a `g_variant_unref(parameters)` call here, but it needs to
    only be done if `parameters` is not `NULL`. This was causing
    frequent "g_variant_unref: assertion 'value != NULL' failed"
    errors in the journal, see
    https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3102 .
    
    Signed-off-by: Adam Williamson <awilliam redhat com>

 libgjs-private/gjs-gdbus-wrapper.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/libgjs-private/gjs-gdbus-wrapper.c b/libgjs-private/gjs-gdbus-wrapper.c
index f73613664..eb0516f99 100644
--- a/libgjs-private/gjs-gdbus-wrapper.c
+++ b/libgjs-private/gjs-gdbus-wrapper.c
@@ -395,7 +395,9 @@ gjs_dbus_implementation_emit_signal (GjsDBusImplementation *self,
 
         g_object_unref(iter->data);
     }
-    g_variant_unref(parameters);
+    if (parameters != NULL)
+        g_variant_unref(parameters);
+
     g_list_free(connections);
 }