Custom titlebar menu disappears after a click on a separator or empty space

[PastorGL]

Issue Type: Bug

1. Update to 1.28 or 1.29. New custom titlebar combined with top-level menu is enabled by default.
2. Open any top-level menu.
3. Click on a separator line or white space before first or after last menu item.

What's desired: menu should stay.

What's wrong: menu disappears.

This is inconsistent with Windows established menu handling pattern. Menus usually don't disappear after a click outside of interactive items, i.e. separators or white space or borders.

VS Code version: Code 1.29.1 (bc24f98, 2018-11-15T19:13:36.375Z)
OS version: Windows_NT x64 10.0.17763

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-4460 CPU @ 3.20GHz (4 x 3193)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: enabled video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled
Memory (System)	15.69GB (5.70GB free)
Process Argv
Screen Reader	no
VM	0%