patch 9.0.0982: 'cursorline' not drawn before virtual text below

Problem:    'cursorline' not drawn before virtual text below.
Solution:   Add the 'cursorline' attribute to the empty space. (closes #11647)

src/testdir/dumps/Test_prop_with_text_below_cul_1.dump

@@ -0,0 +1,6 @@
+>s+8&#ffffff0|o|m|e| |t|e|x|t| @50
+@4|T+8&#ffd7ff255|h|e| |q|u|i|c|k| |b|r|o|w|n| |f|o|x| |j|u|m|p|s| |o|v|e|r| |t|h|e| |l|a|z|y| |d|o|g| +8&#ffffff0@12
+|l+0&&|a|s|t| |l|i|n|e| @50
+|~+0#4040ff13&| @58
+|~| @58
+| +0#0000000&@41|1|,|1| @10|A|l@1| 

src/testdir/test_textprop.vim

@@ -2918,6 +2918,29 @@ func Test_props_with_text_after_nowrap()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_prop_with_text_below_cul()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+      vim9script
+
+      setline(1, ['some text', 'last line'])
+      set cursorline nowrap
+      prop_type_add('test', {highlight: 'DiffChange'})
+      prop_add(1, 0, {
+          type: 'test',
+          text: 'The quick brown fox jumps over the lazy dog',
+          text_align: 'below',
+          text_padding_left: 4,
+      })
+  END
+  call writefile(lines, 'XscriptPropsBelowCurline', 'D')
+  let buf = RunVimInTerminal('-S XscriptPropsBelowCurline', #{rows: 6, cols: 60})
+  call VerifyScreenDump(buf, 'Test_prop_with_text_below_cul_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_props_with_text_below_nowrap()
   CheckRunVimInTerminal