patch 8.2.3810: Vim9: expr4 test fails on MS-Windows

Problem:    Vim9: expr4 test fails on MS-Windows.
Solution:   Do not give an error for a missing function name when skipping.

src/eval.c

@@ -2001,7 +2001,7 @@ eval_func(
     // Need to make a copy, in case evaluating the arguments makes
     // the name invalid.
     s = vim_strsave(s);
-    if (s == NULL || *s == NUL || (flags & EVAL_CONSTANT))
+    if (s == NULL || (evaluate && (*s == NUL || (flags & EVAL_CONSTANT))))
 	ret = FAIL;
     else
     {

src/testdir/test_vim9_expr.vim

@@ -646,8 +646,16 @@ def Test_expr4_equal()
       assert_equal(false, function('g:Test_expr4_equal', [123]) == function('g:Test_expr4_is', [123]))
       assert_equal(false, function('g:Test_expr4_equal', [123]) == function('g:Test_expr4_equal', [999]))
 
-      # TODO: this unexpectedly sometimes fails on Appveyor
-      if !has('win32')
+      if true
+        var OneFunc: func
+        var TwoFunc: func
+        OneFunc = function('len')
+        TwoFunc = function('len')
+        assert_equal(true, OneFunc('abc') == TwoFunc('123'))
+      endif
+
+      # check this doesn't fail when skipped
+      if false
         var OneFunc: func
         var TwoFunc: func
         OneFunc = function('len')

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3810,
 /**/
     3809,
 /**/