patch 9.0.0667: ml_get error when 'splitkeep' is "screen"

Problem:    ml_get error when 'splitkeep' is "screen". (Marius Gedminas)
Solution:   Check the botline is not too large. (Luuk van Baal,
            closes #11293, closes #11292)

src/testdir/test_window_cmd.vim

@@ -1807,6 +1807,13 @@ function Test_splitkeep_misc()
   let top = line('w0')
   help | quit
   call assert_equal(top, line('w0'))
+  " No error when resizing window in autocmd and buffer length changed
+  autocmd FileType qf exe "resize" line('$')
+  cexpr getline(1, '$')
+  copen
+  wincmd p
+  norm dd
+  cexpr getline(1, '$')
 
   %bwipeout!
   set splitbelow&

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    667,
 /**/
     666,
 /**/

src/window.c

@@ -6356,7 +6356,8 @@ win_fix_scroll(int resize)
 	if (wp->w_height != wp->w_prev_height)
 	{
 	    // If window has moved update botline to keep the same screenlines.
-	    if (*p_spk == 's' && wp->w_winrow != wp->w_prev_winrow)
+	    if (*p_spk == 's' && wp->w_winrow != wp->w_prev_winrow
+		      && wp->w_botline - 1 <= wp->w_buffer->b_ml.ml_line_count)
 	    {
 		lnum = wp->w_cursor.lnum;
 		diff = (wp->w_winrow - wp->w_prev_winrow)