vim-patch:8.2.1919: assert_fails() setting emsg_silent changes normal execution (#20998)

Problem:    Assert_fails() setting emsg_silent changes normal execution.
Solution:   Use a separate flag in_assert_fails.

28ee892ac4

Cherry-pick no_wait_return from patch 9.0.0846.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/normal.c

@@ -611,6 +611,7 @@ static bool normal_need_redraw_mode_message(NormalState *s)
           && stuff_empty()
           && typebuf_typed()
           && emsg_silent == 0
+          && !in_assert_fails
           && !did_wait_return
           && s->oa.op_type == OP_NOP);
 }