[evince/fix_criticals_label_absence] don't set label property with a NULL value

[Nelson Ben <nbenitez src gnome org>]

commit 42366c31bc9c0ec68888f9867b52aeb934b3a3b2
Author: Nelson Benítez León <nbenitezl gmail com>
Date:   Sat Jun 25 22:13:30 2022 +0100

    don't set label property with a NULL value
    
    in ev_annot_from_poppler_annot() function of
    ev-poppler.c because otherwise a critical
    message will be printed to the console.
    
    Fixes #1814

 backend/pdf/ev-poppler.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/backend/pdf/ev-poppler.c b/backend/pdf/ev-poppler.c
index b87673412..bc4813140 100644
--- a/backend/pdf/ev-poppler.c
+++ b/backend/pdf/ev-poppler.c
@@ -2979,10 +2979,11 @@ ev_annot_from_poppler_annot (PopplerAnnot *poppler_annot,
                        }
 
                        label = poppler_annot_markup_get_label (markup);
+                       if (label)
+                               g_object_set (ev_annot, "label", label, NULL);
                        opacity = poppler_annot_markup_get_opacity (markup);
 
                        g_object_set (ev_annot,
-                                     "label", label,
                                      "opacity", opacity,
                                      "can_have_popup", TRUE,
                                      NULL);