patch 8.2.1729: endless loop when ":normal" feeds popup window filter

Problem:    Endless loop when ":normal" feeds popup window filter.
Solution:   Add the ex_normal_busy_done flag.
diff --git a/src/getchar.c b/src/getchar.c
index e42fc33..2c7bd1f 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1888,7 +1888,7 @@
     }
 #endif
 #ifdef FEAT_PROP_POPUP
-    if (popup_do_filter(c))
+    if (!ex_normal_busy_done && popup_do_filter(c))
     {
 	if (c == Ctrl_C)
 	    got_int = FALSE;  // avoid looping
@@ -3168,6 +3168,10 @@
 			timedout = TRUE;
 			continue;
 		    }
+#ifdef FEAT_PROP_POPUP
+		    ex_normal_busy_done = TRUE;
+#endif
+
 		    // When 'insertmode' is set, ESC just beeps in Insert
 		    // mode.  Use CTRL-L to make edit() return.
 		    // For the command line only CTRL-C always breaks it.