* src/frame.c (make_monitor_attribute_list): Allow source to be NULL.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/frame.c b/src/frame.c
index 36a256f1f3d..286c9a2cb71 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -6138,8 +6138,11 @@ make_monitor_attribute_list (struct MonitorInfo *monitors,
                          mi->work.width, mi->work.height);
       geometry = list4i (mi->geom.x, mi->geom.y,
                          mi->geom.width, mi->geom.height);
-      attributes = Fcons (Fcons (Qsource, build_string (source)),
-                          attributes);
+
+      if (source)
+        attributes = Fcons (Fcons (Qsource, build_string (source)),
+                            attributes);
+
       attributes = Fcons (Fcons (Qframes, AREF (monitor_frames, i)),
                           attributes);
 #ifdef HAVE_PGTK