vim-patch:8.2.3611: crash when using CTRL-W f without finding a file name

Problem:    Crash when using CTRL-W f without finding a file name.
Solution:   Bail out when the file name length is zero.
615ddd5342

src/nvim/testdir/test_visual.vim

@@ -1123,6 +1123,14 @@ func Test_visual_block_with_virtualedit()
   call delete('XTest_block')
 endfunc
 
+func Test_visual_block_ctrl_w_f()
+  " Emtpy block selected in new buffer should not result in an error.
+  au! BufNew foo sil norm f
+  edit foo
+
+  au! BufNew
+endfunc
+
 func Test_visual_reselect_with_count()
   " this was causing an illegal memory access
   let lines =<< trim END