patch 7.4.2233

Problem:    Crash when using funcref() with invalid name. (Dominique Pelle)
Solution:   Check for NULL translated name.

src/testdir/test_expr.vim

@@ -237,6 +237,7 @@ func Test_funcref()
   call assert_equal(1, OneByRef())
   let OneByRef = funcref('One')
   call assert_equal(2, OneByRef())
+  call assert_fails('echo funcref("{")', 'E475:')
 endfunc
 
 func Test_setmatches()