vim-patches: 8.0.0399 8.0.0401 (#8475)

vim-patch:8.0.0399: crash when using balloon_show() when not supported
Problem:    Crash when using balloon_show() when not supported. (Hirohito
            Higashi)
Solution:   Check for balloonEval not to be NULL. (Ken Takata)
https://github.com/vim/vim/commit/caf6434ac937cf26050276d7b474be2d2d6a06b3

vim-patch:8.0.0401: test fails with missing balloon feature
Problem:    Test fails with missing balloon feature.
Solution:   Add check for balloon feature.
https://github.com/vim/vim/commit/a0107bdf8762d81cb49909ef02ffff9954092fb6

vim-patch:8.0.0414: balloon eval is not tested

src/nvim/testdir/test_functions.vim

@@ -759,3 +759,10 @@ func Test_col()
   call assert_equal(0, col([1]))
   bw!
 endfunc
+
+func Test_balloon_show()
+  if has('balloon_eval')
+    " This won't do anything but must not crash either.
+    call balloon_show('hi!')
+  endif
+endfunc