patch 9.0.0079: error in autoload script not reported for 'foldexpr'

Problem:    Error in autoload script not reported for 'foldexpr'.
Solution:   Reset "emsg_off" when auto-loading a script. (closes #10685)

src/testdir/test_vim9_script.vim

@@ -3440,6 +3440,30 @@ def Test_error_in_autoload_script()
   delete(dir, 'rf')
 enddef
 
+def Test_error_in_autoload_script_foldexpr()
+  var save_rtp = &rtp
+  mkdir('Xvim/autoload', 'p')
+  &runtimepath = 'Xvim'
+
+  var lines =<< trim END
+      vim9script
+      eval [][0]
+      echomsg 'no error'
+  END
+  lines->writefile('Xvim/autoload/script.vim')
+
+  lines =<< trim END
+      vim9script
+      import autoload 'script.vim'
+      &foldmethod = 'expr'
+      &foldexpr = 'script.Func()'
+      redraw
+  END
+  v9.CheckScriptFailure(lines, 'E684: List index out of range: 0')
+
+  delete('Xvim', 'rf')
+enddef
+
 def Test_invalid_sid()
   assert_fails('func <SNR>1234_func', 'E123:')
 

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    79,
 /**/
     78,
 /**/

src/vim9compile.c

@@ -611,11 +611,19 @@ find_imported(char_u *name, size_t len, int load)
     if (ret != NULL && load && (ret->imp_flags & IMP_FLAGS_AUTOLOAD))
     {
 	scid_T	dummy;
+	int	save_emsg_off = emsg_off;
+
+	// "emsg_off" will be set when evaluating an expression silently, but
+	// we do want to know about errors in a script.  Also because it then
+	// aborts when an error is encountered.
+	emsg_off = FALSE;
 
 	// script found before but not loaded yet
 	ret->imp_flags &= ~IMP_FLAGS_AUTOLOAD;
 	(void)do_source(SCRIPT_ITEM(ret->imp_sid)->sn_name, FALSE,
 							    DOSO_NONE, &dummy);
+
+	emsg_off = save_emsg_off;
     }
     return ret;
 }