patch 8.1.1573: textprop test fails if screenhots do not work

Problem:    Textprop test fails if screenhots do not work.
Solution:   Add check for screenhots working.
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 36eeb70..df060ea 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -760,6 +760,10 @@
 endfunc
 
 func Test_textprop_after_tab()
+  if !CanRunVimInTerminal()
+    throw 'Skipped: cannot make screendumps'
+  endif
+
   let lines =<< trim END
        call setline(1, [
              \ "\txxx",
diff --git a/src/version.c b/src/version.c
index 62ef113..9060ceb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1573,
+/**/
     1572,
 /**/
     1571,