patch 8.2.4098: typing "interrupt" at debug prompt may keep exception around

Problem:    Typing "interrupt" at debug prompt may keep exception around,
            causing function calls to fail.
Solution:   Discard any exception at the toplevel. (closes #9532)
diff --git a/src/main.c b/src/main.c
index 8f3856f..72d0211 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1246,6 +1246,13 @@
 	else
 	    previous_got_int = FALSE;
 
+#ifdef FEAT_EVAL
+	// At the toplevel there is no exception handling.  Discard any that
+	// may be hanging around (e.g. from "interrupt" at the debug prompt).
+	if (did_throw && !ex_normal_busy)
+	    discard_current_exception();
+#endif
+
 	if (!exmode_active)
 	    msg_scroll = FALSE;
 	quit_more = FALSE;