patch 7.4.1329
Problem:    Crash when using channel that failed to open.
Solution:   Check for NULL.  Update messages. (Yukihiro Nakadaira)
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index e7448fa..7cc3f14 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -318,3 +318,9 @@
 func Test_unlet_handle()
   call s:run_server('s:unlet_handle')
 endfunc
+
+func Test_open_fail()
+  silent! let ch = ch_open("noserver")
+  echo ch
+  let d = ch
+endfunc