patch 8.2.1714: text properties corrupted with substitute command

Problem:    Text properties corrupted with substitute command. (Filipe
            Brandenburger)
Solution:   Get the changed line again after using u_savesub(). (closes #6984)
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 5bd7e95..dbf393f 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -1132,6 +1132,19 @@
   bwipe!
 endfunc
 
+" This was causing property corruption.
+func Test_proptype_substitute3()
+  new
+  call setline(1, ['abcxxx', 'def'])
+  call prop_type_add("test", {"highlight": "Search"})
+  call prop_add(1, 2, {"end_lnum": 2, "end_col": 2, "type": "test"})
+  %s/x\+$//
+  redraw
+
+  call prop_type_delete('test')
+  bwipe!
+endfunc
+
 func SaveOptions()
   let d = #{tabstop: &tabstop,
 	  \ softtabstop: &softtabstop,