patch 9.0.0318: clearing screen causes flicker

Problem:    Clearing screen causes flicker.
Solution:   Do not clear but redraw in more cases.  Add () to "wait_return".
diff --git a/src/memline.c b/src/memline.c
index 3911213..6651cda 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -822,7 +822,7 @@
 
     if (*p_dir != NUL && mfp->mf_fname == NULL)
     {
-	need_wait_return = TRUE;	// call wait_return later
+	need_wait_return = TRUE;	// call wait_return() later
 	++no_wait_return;
 	(void)semsg(_(e_unable_to_open_swap_file_for_str_recovery_impossible),
 		    buf_spname(buf) != NULL ? buf_spname(buf) : buf->b_fname);