patch 9.0.0130: cursor position wrong when inserting around virtual text

Problem:    Cursor position wrong when inserting around virtual text.
Solution:   Update the cursor position properly.

src/testdir/test_textprop.vim

@@ -2256,4 +2256,20 @@ func Test_removed_prop_with_text_cleans_up_array()
   bwipe!
 endfunc
 
+def Test_insert_text_before_virtual_text()
+  new foobar
+  setline(1, '12345678')
+  prop_type_add('test', {highlight: 'Search'})
+  prop_add(1, 5, {
+    type: 'test',
+    text: ' virtual text '
+    })
+  normal! f4axyz
+  normal! f5iXYZ
+  assert_equal('1234xyzXYZ5678', getline(1))
+
+  prop_type_delete('test')
+  bwipe!
+enddef
+
 " vim: shiftwidth=2 sts=2 expandtab