patch 9.1.0098: CompletionChanged not triggered when new leader added without matches

Problem:  CompletionChanged not triggered when new leader added causing
          no matching item in the completion menu
Solution: When completion is active but no items matched still trigger
          CompletChanged event
          (glepnir)

closes: #13982

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/insexpand.c b/src/insexpand.c
index d712181..68e970a 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -1350,7 +1350,13 @@
     }
 
     if (compl_match_array == NULL)
+    {
+#ifdef FEAT_EVAL
+	if (compl_started && has_completechanged())
+	    trigger_complete_changed_event(cur);
+#endif
 	return;
+    }
 
     // In Replace mode when a $ is displayed at the end of the line only
     // part of the screen would be updated.  We do need to redraw here.