patch 8.2.0839: dropping modifier when putting a character back in typeahead

Problem:    Dropping modifier when putting a character back in typeahead.
Solution:   Add modifier to ins_char_typebuf(). (closes #6158)
diff --git a/src/terminal.c b/src/terminal.c
index 52f8105..59bf039 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -3467,7 +3467,7 @@
 	redraw_statuslines();
 
 	// Need to break out of vgetc().
-	ins_char_typebuf(K_IGNORE);
+	ins_char_typebuf(K_IGNORE, 0);
 	typebuf_was_filled = TRUE;
 
 	term = curbuf->b_term;