--- a/sat_frontends/quick_frontend/quick_widgets.py	Fri Jan 17 17:55:57 2020 +0100
+++ b/sat_frontends/quick_frontend/quick_widgets.py	Fri Jan 17 18:47:02 2020 +0100
@@ -255,6 +255,10 @@
                 if widget is None:
                     raise exceptions.InternalError(
                         "on_existing_widget method must return the widget to use")
+                if widget not in widgets_map[hash_]:
+                    log.debug(
+                        "the widget returned by on_existing_widget is new, adding it")
+                    widgets_map[hash_].append(widget)
             else:
                 raise exceptions.InternalError(
                     "Unexpected on_existing_widget value ({})".format(on_existing_widget))
@@ -299,7 +303,11 @@
             return
         widget_hash = str(class_.getWidgetHash(widget_to_delete.target,
                                                    widget_to_delete.profiles))
-        widget_instances = widgets_map[widget_hash]
+        try:
+            widget_instances = widgets_map[widget_hash]
+        except KeyError:
+            log.error(f"no instance of {class_.__name__} found with hash {widget_hash!r}")
+            return
         if all_instances:
             widget_instances.clear()
         else:
@@ -315,7 +323,7 @@
             # all instances with this hash have been deleted
             # we remove the hash itself
             del widgets_map[widget_hash]
-            log.debug("All instances of {cls} with hash {widget_hash} have been deleted"
+            log.debug("All instances of {cls} with hash {widget_hash!r} have been deleted"
                 .format(cls=class_, widget_hash=widget_hash))