vim-patch:8.2.1939: invalid memory access in Ex mode with global command

Problem:    Invalid memory access in Ex mode with global command.
Solution:   Make sure the cursor is on a valid line. (closes vim/vim#7238)

3b6d57f2ce

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

src/nvim/move.c

@@ -259,6 +259,7 @@ void update_topline(win_T *wp)
   // If there is no valid screen and when the window height is zero just use
   // the cursor line.
   if (!default_grid.chars || wp->w_view_height == 0) {
+    check_cursor_lnum(wp);
     wp->w_topline = wp->w_cursor.lnum;
     wp->w_botline = wp->w_topline;
     wp->w_viewport_invalid = true;

test/old/testdir/test_ex_mode.vim

@@ -259,6 +259,30 @@ func Test_ex_mode_errors()
   quit
 endfunc
 
+func Test_ex_mode_with_global()
+  CheckFeature timers
+
+  " This will get stuck in Normal mode after the failed "J", use a timer to
+  " get going again.
+  let lines =<< trim END
+    " call ch_logfile('logfile', 'w')
+    pedit
+    func FeedQ(id)
+      call feedkeys('gQ', 't')
+    endfunc
+    call timer_start(10, 'FeedQ')
+    g/^/vi|HJ
+    call writefile(['done'], 'Xdidexmode')
+    qall!
+  END
+  call writefile(lines, 'Xexmodescript')
+  call assert_equal(1, RunVim([], [], '-e -s -S Xexmodescript'))
+  call assert_equal(['done'], readfile('Xdidexmode'))
+
+  call delete('Xdidexmode')
+  call delete('Xexmodescript')
+endfunc
+
 func Test_ex_mode_count_overflow()
   " The multiplication causes an integer overflow
   CheckNotAsan