patch 8.2.3910: when compare function of sort() fails it does not abort

Problem:    When the compare function of sort() produces and error then sort()
            does not abort.
Solution:   Check if did_emsg was incremented.

src/list.c

@@ -1919,6 +1919,7 @@ item_compare2(const void *s1, const void *s2)
     char_u	*func_name;
     partial_T	*partial = sortinfo->item_compare_partial;
     funcexe_T	funcexe;
+    int		did_emsg_before = did_emsg;
 
     // shortcut after failure in previous call; compare all items equal
     if (sortinfo->item_compare_func_err)
@@ -1946,7 +1947,7 @@ item_compare2(const void *s1, const void *s2)
     clear_tv(&argv[0]);
     clear_tv(&argv[1]);
 
-    if (res == FAIL)
+    if (res == FAIL || did_emsg > did_emsg_before)
 	res = ITEM_COMPARE_FAIL;
     else
     {

src/testdir/test_vim9_builtin.vim

@@ -3524,6 +3524,17 @@ def Test_sort_argument()
   CheckDefAndScriptFailure(['sort([1], "", [1])'], ['E1013: Argument 3: type mismatch, expected dict<any> but got list<number>', 'E1206: Dictionary required for argument 3'])
 enddef
 
+def Test_sort_compare_func_fails()
+  var lines =<< trim END
+    vim9script
+    echo ['a', 'b', 'c']->sort((a: number, b: number) => 0)
+  END
+  writefile(lines, 'Xbadsort')
+  assert_fails('source Xbadsort', ['E1013:', 'E702:'])
+
+  delete('Xbadsort')
+enddef
+
 def Test_spellbadword()
   CheckDefAndScriptFailure(['spellbadword(100)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
   spellbadword('good')->assert_equal(['', ''])

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3910,
 /**/
     3909,
 /**/