patch 7.4.1255
Problem:    Crash for channel "eval" command without third argument.
Solution:   Check for missing argument.
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index b416520..3caf5d2 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -90,6 +90,10 @@
   call assert_equal('ok', ch_sendexpr(handle, 'eval-fails'))
   call assert_equal([-2, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
 
+  " Send a bad eval request. There will be no response.
+  call assert_equal('ok', ch_sendexpr(handle, 'eval-bad'))
+  call assert_equal([-2, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
+
   " make the server quit, can't check if this works, should not hang.
   call ch_sendexpr(handle, '!quit!', 0)