patch 8.2.1237: changing 'completepopup' after opening popup has no effect

Problem:    Changing 'completepopup' after opening a popup has no effect. (Jay
            Sitter)
Solution:   Close the popup when the options are changed. (closes #6471)
diff --git a/src/optionstr.c b/src/optionstr.c
index a0409fa..bfc2e3b 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -2249,6 +2249,8 @@
     {
 	if (parse_completepopup(NULL) == FAIL)
 	    errmsg = e_invarg;
+	else
+	    popup_close_info();
     }
 # endif
 #endif