cannot select port & cannot open port

[VulcanLIU]

Issue Type: Bug

when I click "",My Visual code doesn't popup the list of COM as before.I type "port": "COM3" in arduino.json by hand and try to open port.My Visual code told me ”Failed to open serial port com3 due to error: + TypeError: Cannot read property 'close' of null”. My arudino IDE version is 1.8.9. Extension version: 0.2.29 VS Code version: Code 1.43.0 (78a4c91400152c0f27ba4d363eb56d2835f9903a, 2020-03-09T19:47:57.235Z) OS version: Windows_NT x64 10.0.18363 System Info Item Value CPUs Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz (8 x 2592) GPU Status 2d_canvas: enabledflash_3d: enabledflash_stage3d: enabledflash_stage3d_baseline: enabledgpu_compositing: enabledmultiple_raster_threads: enabled_onoop_rasterization: disabled_offprotected_video_decode: unavailable_offrasterization: enabledskia_renderer: disabled_off_okvideo_decode: enabledviz_display_compositor: enabled_onviz_hit_test_surface_layer: disabled_off_okwebgl: enabledwebgl2: enabled Load (avg) undefined Memory (System) 7.89GB (3.51GB free) Process Argv C:\Users\Vulca\Desktop\1\1 Screen Reader no VM 0%

[dilin-MS]

Duplicate with #980